Nail Knobs, Split Knobs
and Other House Wiring
Knob Insulators
Nail knobs were commonly used for house wiring, which had an insulated covering. Wall tubes were also used to go through studs and rafters. Here are few photos that show how they were used. Not all the split knobs shown on this web page are "nail knobs" as many styles were intended to be mounted with wood screws.
This link is an interesting video that shows an example of how knobs and cleats were used together: https://youtu.be/x8ekfxijhuA
Below is a listing of nail knobs in my collection. Please note the following legend when reading the table. Click on the Category Number to see a photo of the insulator or go to the pages with photos of all insulators listed below:
R = round (standard diameter) nail knob
RR = round reversible knob (see Nail Knob Page 2)
O = oval (see Nail Knob Page 2)
S = square or rectangular (see Nail Knob Page 2)
SR = square or rectangular reversible knob (see Nail Knob Page 2)
/ = marking on opposite side
// = marking on bottom
Patents for Knobs - Click on this link to see a list of all the knob patents.
| Category No. |
MARKING | Marking Type | Patent | Company | Notes | |
|---|---|---|---|---|---|---|
| Nail Knobs | ||||||
| R-132 |
  |
( ?? ) | 1-3/16" diameter; thick bottom with 3 firing rest teats | |||
| R-27 |
 |
(illegible patent date) | emb | 907,251 | Colonial Sign & Insulator Co. | specimen found at Colonial |
| R-102 |
 
 |
2 (top) // 4 (under bottom) | emb | 1-1/8" diameter | ||
| R-112 (don't have) |
  |
ALLIGATOR | (Porcelain Products Inc.) | radial ribs under cap | ||
| R-56 |
|
A P C L | r-e | 917207 | 1" diameter (possibly made by Thomas, see R-45) | |
| R-32 |
 |
A. P. CO. G. E. CO. 9419 (circle) | emb | Anderson Porcelain Co. | cap only; 1-1/2" diameter | |
| R-55 |
|
B & D JR / PAT 9-3-07 // B | emb | 864,947 | 1" diameter | |
| R-66 |
|
B & D PAT // K | emb/r-e | 1" diameter; 1 wire; offset nail | ||
| R-73 |
|
B & D | emb | 1" diameter | ||
| R-101 |
  |
B.&.D. / PAT. / IMP / 07. | emb | Buffinton & Dow | Imperial Porcelain Works; 1-1/8" | |
| R-02 |
  |
BMOCAM (Macomb) | emb | Illinois Electric Porcelain Co. | matching V-grooves on cap and base | |
| R-18 |
  |
BRUNT (backward N) | emb | 917,207 | Brunt Porcelain Co. | 1" diameter, nail hole offset; matching V-grooves |
| R-82 |
   |
BRUNT / CINCH | emb | G. F. Brunt Porcelain Co. | radially ribbed cap; captivated nail | |
| R-121 |
|
BRUNT / CINCH // BRUNT | emb | G. F. Brunt Porcelain Co. | 1" diamter; radially ribbed cap; captivated nail | |
| R-15 |
|
BRUNT / CINCH // BRUNT | emb | G. F. Brunt Porcelain Co. | radially ribbed cap; captivated nail | |
| R-116 |
 |
BRUNT / PAT-FEB-3-1920 | emb | 1,329,656 | G. F. Brunt Porcelain Co. | radially ribbed cap |
| R-131 |
 |
BRUNT / PAT-FEB-3-1920 | emb | 1,329,656 | G. F. Brunt Porcelain Co. | radially ribbed cap |
| R-160 |
  |
BRUNT (slanted caming cap) | emb | 464,770 | Brunt Porcelain Co. | 1-1/2" x 1-7/8" tall |
| R-157 |
  |
BULL OG (should be DOG) (btm) | emb | Illinois Electric Porcelain Co. | radially ribbed cap, captivated nail | |
| R-76 |
 
  |
C (B on bottom edge) | r-e | 1" diameter | ||
| R-89 |
  |
C / 800 / C (dot inside each C) | emb | 1-1/8" diameter, unglazed | ||
| R-113 |
  |
CAREY / OHIO | emb | Carey Ohio Porcelain Co. | Concentric rings under cap | |
| R-85 |
 
 |
CCE / D // CCE / D | inc/r-e | 1-1/8" x 1-1/2" (Canadian) | ||
| R-148 |
 |
CLINCHO // PAT. APPL'D FOR (btm) | emb/r-e | Mogadore Insulator Co. | 1-3/8" diameter; 1-7/8" tall | |
| R-115 |
  |
CORWICO / USA | emb | |||
| R-96 |
 |
C:S:I:CO / AKRON (in recessed band; cap projection) | r-e | Colonial Sign & Insulator Co. | 1-3/16" diameter | |
| R-79 |
 |
DIXIE SCREW-IT PAT.JAN.7,1919. | emb | 1,290,540 | J. H. Parker & Son | 1-3/16" diameter; 6-prong star under cap |
| R-80 |
 |
DIXIE NAILIT PAT. JAN.7,1919-FEB.3,1920. | emb | 1,290,440 and 1,329,656 | J. H. Parker & Son | 1-3/16" diameter; 6-prong star under cap |
| R-44 |
  |
D P Co / EVER READY (in circle) | r-e | Davidson Porcelain Co. | concentric rings under cap | |
| R-154 |
 |
D & S | emb | Davidson & Stevenson | 1-1/8" diameter x 1-5/8" tall | |
| R-62 |
  |
EFFICIENCY | emb | The Efficiency Electrical Co. | center extends down inside the bottom | |
| R-68 |
    |
F (under bottom) | emb | 1-1/8" diameter; boxed projection on cap fits in bottom | ||
| R-127 |
   |
F // F (under bottom) | emb | Findlay Electric Porcelain Co. | 1-1/8" diameter; boxed projection on cap fits in bottom | |
| R-12 |
|
FEDCO | emb | Federal Porcelain Co. | corrugated cap; captivated nail | |
| R-126 |
  |
FEDCO | emb | Federal Porcelain Co. | 1-3/16" diameter, flat top, corrugated cap; captivated nail | |
| R-92 |
  |
FEDCO | emb | Federal Porcelain Co. | corrugated cap; captivated nail | |
| R-103 |
  |
FEDCO PAT. 1.16.12. | emb | Federal Porcelain Co. | 1-1/8" corrugated cap; captivated nail | |
| R-114 |
 |
FEDCO PAT. 1.16.12. | emb | Federal Porcelain Co. | 1-1/8" corrugated cap; captivated nail | |
| R-42 |
   |
FINDLAY (backward N) / ALLIGATOR | emb | Findlay Electric Porcelain Co. | corrugated cap | |
| R-152 |
 |
FINDLAY NO. 1911 // PAT. 5-6-13 | emb | 1,060,886 | Findlay Electric Porcelain Co. | |
| R-43 |
  |
G | emb | 917,207 | 1" diameter, nail hole offset; matching V-grooves on cap and base | |
| R-172 |
  |
G E CO.USA. CAT.48519 | emb | 917,207 | General Electric Co. | 1" diameter, nail hole offset; V-grooves on cap and base |
| R-137 |
 |
G.E.CO.U.S.A / CAT.48520 | emb | General Electric Co. | 1-1/8" diameter, 2 grooves with slotted cap | |
| R-41 |
  |
GEE PEE | emb | General Porcelain Co. | radially ribbed cap | |
| R-31 |
  |
GRIP IT / PAT. | r-e | 1,429,369 | J. H. Parker & Son | cap only |
| R-84 |
  |
GRIPIT / G. P. CO. PATD | r-e | 1,429,369 | General Porcelain Co. | 1-1/8" diameter; made for J. H. Parker & Son |
| R-17 |
   |
IDEAL // PATENTED / 5 28 07 | emb/r-e | 855,208 | Star Porcelain Co. | |
| R-94 |
  |
KNOX (in recessed band) | r-e | Knox Porcelain Corp. | 1-1/8" diameter | |
| R-54 |
|
KNOX / 5 1/2 | r-e | Knox Porcelain Corp. | 1-1/8" diameter | |
| R-118 (don't have) |
 |
KNOX / 5 1/2 | r-e | Knox Porcelain Corp. | 1-1/8" diameter | |
| R-86 |
  |
KNOX / KNOB | r-e | Knox Porcelain Corp. | 1-1/8" diameter | |
| R-99 |
  |
KNOX / KNOB | r-e | Knox Porcelain Corp. | 1-1/8" diameter | |
| R-100 |
  |
KNOX / NAILIT | r-e | Knox Porcelain Corp. | 1-1/8" diameter | |
| R-95 |
  |
KNOX PAT. APPLD FOR (in recessed band) | r-e | Knox Porcelain Corp. | 1-1/8" diameter | |
| R-01 |
  |
MACOMB | emb | Illinois Electric Porcelain Co. | ||
| R-16 |
  |
MACOMB | emb | Illinois Electric Porcelain Co. | ribbed channels in cap and base | |
| R-11 |
 
|
MONOWATT | emb | ?? | concentric ring under cap; captivated nail | |
| R-123 |
   |
N (cap) // N (under bottom) | emb | National Electric Porcelain Co. | 1" diameter | |
| R-128 |
  |
N (in trough of base) [no cap] | emb | National Electric Porcelain Co. | 1-1/4" diameter; shown in Trenton Porcelain catalog as "Detroit split insulator" | |
| R-14 |
|
NAILIT / PAT APPLD FOR | r-e | 1,329,656 | J. H. Parker & Son | radially ribbed cap; captivated nail |
| R-98 |
  |
NAILIT / PAT APPLD FOR | emb | 1,329,656 | J. H. Parker & Son | radially ribbed cap; captivated nail |
| R-117 |
  |
NAILIT / PAT.APPLD.FOR (backward N) | emb | 1,329,656 | J. H. Parker & Son | radially ribbed cap; captivated nail |
| R-108 (don't have) |
  |
NAILIT / PAT-APPLD.FOR. | r-e | 1,329,656 | J. H. Parker & Son | radially ribbed cap; captivated nail |
| R-35 |
 |
NAILIT / PAT FEB. 3, 1920 (backward N) | emb | 1,329,656 | J. H. Parker & Son | radially ribbed cap |
| R-71 |
  |
NAILIT. / PAT. 2 3, 1920 | emb | 1,329,656 | J. H. Parker & Son | 1-3/16" diameter; radially ribbed cap |
| R-119 |
  |
NAILIT. / PAT. 2 3. 1920. | r-e | 1,329,656 | J. H. Parker & Son | 1-3/16" diameter; concentric ribbed cap |
| R-122 (don't have) |
  |
NAILIT. / PAT. 2. 3. 1920. | emb | 1,329,656 | J. H. Parker & Son | 1-3/16" diameter; concentric ribbed cap |
| R-50 |
|
NAT / READY | emb | National Electric Porcelain Co. | 1-1/8" diameter; radial ribs under cap | |
| R-39 |
  |
NAT. / READY / PAT / 2-3-20. | emb | 1,329,656 | National Electric Porcelain Co. | unglazed; radially ribbed cap; captivated nail; 1-3/16" diameter x 1-3/4" tall |
| R-155 |
 |
NAT. / READY / PAT / 2-3-20. // N | emb | 1,329,656 | National Electric Porcelain Co. | glazed; radially ribbed cap; captivated nail;1-3/16" diameter x 1-3/4" tall |
| R-06 |
  |
N-N | cone top, cone recessed bottom; corrugated cap with raised ring around outside; captivated nail | |||
| R-133 |
 
 |
N-N | cone-shaped cap with concentric ribbs underneath | |||
| R-08 |
 |
N-N | rounded top, cone recessed bottom | |||
| R-09 |
  |
N-N | rounded top, deep recessed bottom | |||
| R-26 |
   |
N-N | 965,723 | Paragon Electric Co. | ball fits on top of the base | |
| R-28 |
|
N-N | 907,251 | Colonial Sign & Insulator Co. | ||
| R-57 |
|
N-N | 1-3/16" diameter | |||
| R-75 |
|
N-N | 1" diameter | |||
| R-124 (don't have) |
   |
N-N | ||||
| R-81 |
  |
N-N (Brookman patent) | 1,640,815 | Trenle Porcelain Co. | 1-3/16"; off-set nail, white glazed; It was called the "Quickon" knob | |
| R-110 (don't have) |
  |
N-N (top of cap recessed with spokes) | ||||
| R-156 |
|
N-N (cap has long projection to fit in slot) | 1-3/16" diameter by 1-3/4" tall, captured nail | |||
| R-159 |
|
N-N (slanted caming cap) | 464,770 | Brunt Porcelain Co.(??) | 1-1/2" x 1-5/8" tall | |
| R-105 |
  |
O.I.&C.CO. | r-e | Octagon Insulator & Ceramic Co. | 1-1/8" diameter | |
| R-05 |
  |
P.P. INC. / ALLIGATOR | emb | Porcelain Products Inc. | captivated nail with "12" embossed on nail head; corrugated under cap with raised ring around outside | |
| R-37 |
  |
P.P. INC. / ALLIGATOR / 5½ | emb | Porcelain Products Inc. | captivated nail | |
| R-97 |
  |
P.P. INC. / ALLIGATOR / 5½ | emb | Porcelain Products Inc. | captivated nail | |
| R-87 |
  |
P. P. INC. / 9420 | emb | Porcelain Products Inc. | 2" diameter | |
| R-149 |
 
  |
PAT / 11-29-10 | emb | 977,262 | 1" x 2-3/8" | |
| R-147 |
 |
PAT. APL'D FOR. | emb | 1-5/8" diameter; 1-7/8" tall | ||
| R-146 |
 |
PATD | emb | 511,612 | The Hammond Cleat & Insulator Co. | 1-5/16" diameter; 1-3/8" tall |
| R-30 |
  
 |
PATD - FEB - 3 - 1920 (circle) // PATD / F (under bottom) | emb | 1,329,656 | Illinois Electric Porcelain Co. | cap corrugated underneath; bottom unglazed; captivated nail |
| R-104 (don't have) |
 |
PATD FEB -3-1920- (circle) | emb | 1,329,656 | Illinois Electric Porcelain Co. | |
| R-49 |
|
PAT'D / 10-22-12. | emb | 1,042,372 | 1-1/8" diameter | |
| R-58 |
|
PAT'D / FEB 26 1907 | r-e | 845,544 | The Electric Good Mfg Co. | 1-1/8" diameter |
| R-33 |
 
 
 |
PAT'D / JULY / 19 - 92 (on side) | emb | 479,134 | Conover patent | |
| R-88 |
  |
N-N // PATENT PENDING (under bottom) | emb | 965,723 | Paragon Electric Co. | ball fits on top of the base |
| R-52 |
|
PATENT / PENDING / M | emb | 1-3/16" diameter | ||
| R-29 |
 |
PATENTED MAY 13 1902 (circle on top) | r-e | 699,761 | 1-5/8" diameter; 1-1/2" tall; lightning rod insulator | |
| R-151 |
 |
PATENTED MAY 13. 1902. (circle on top) // KRETZER / BRAND (underneath) | r-e | 699,761 | 1-5/8" diameter; 1-1/2" tall; lightning rod insulator | |
| R-134 |
  |
PATENT APPLIED FOR (circle on top) | r-e | 699,761 | 1-5/8" diameter; 1-1/2" tall; patent is May 13, 1902; lightning rod insulator | |
| R-48 |
 
|
PHILCO | r-e | Philco Radio Corp. | Black glaze | |
| R-34 |
 
 |
POLK / PAT'D MCH 10 | emb | 724,329 | Top is 2-1/4" in diameter with three flanges on top for tying wire around the knob; saw-toothed bottom edge prevents turning; patent date is March 31, 1903 | |
| R-90 |
  |
PSW / 110 / UL | r-e | Specialty Porcelain Works | 1-1/8" diameter, typo of R-07 (SPW); concentric rings under cap; captivated nail | |
| R-63 |
  |
R P CO | emb | 1-3/16" diameter | ||
| R-51 |
|
S (on bottom) | emb | 1" diameter | ||
| R-77 |
 
  |
S - S (S S under bottom) | r-e/emb | 1-1/2" diameter | ||
| R-153 |
 |
S C P CO. | emb | |||
| R-67 |
  |
S P | emb | 1-1/8" diameter | ||
| R-19 |
|
SPW (inside a diamond) | emb | Specialty Porcelain Works | 3/4" diameter, unglazed | |
| R-07 |
  |
SPW / UL / 110 | r-e | Specialty Porcelain Works | concentric rings under cap; captivated nail | |
| R-03 |
  |
SUPERIOR / 5½ | emb | Superior Porcelain Co. | corrugated cap and ring outside; captivated nail | |
| R-45 |
  |
T | emb | 917,207 | R. Thomas & Sons Co. | 1" diameter, nail hole offset; matching slot (see Weber R-135) |
| R-78 |
     |
T in a circle recessed in a square | r-e | Trumbull Electric Mfg. Co. | 1-3/16" diameter | |
| R-83 |
  |
THOMAS | emb | R. Thomas & Sons Co. | 1-3/16" diameter | |
| R-130 |
  |
THOMAS | r-e | R. Thomas & Sons Co. | 1-3/16" diameter; concentric rings under cap | |
| R-169 |
 |
THOMAS | emb | R. Thomas & Sons Co. | 1-3/16" diameter; concentric rings under cap | |
| R-173 |
 |
THOMAS / MADE IN U.S.A. | r-e | R. Thomas & Sons Co. | 1-3/16" diameter | |
| R-38 |
|
T - P - CO. / JIFFY / No 1 // PATD 12-8-03 | emb | 745,999 | Trenton Porcelain Co. | Patent shows a ball top part, but this is a standard-looking nail knob. Raised ring under cap; captivated nail |
| R-74 |
|
T - P - CO. / JIFFY / No 2 // PATD 12-8-03 | emb | 745,999 | Trenton Porcelain Co. | Patent shows a ball top part, but this is a standard-looking nail knob. Raised ring under cap; captivated nail |
| R-70 |
 |
T - P - CO. - MIDGET - 80 - (in circle) | emb | Trenton Porcelain Co. | 1" diameter; cap only | |
| R-69 |
  |
T. P. CO. / 80 | emb | Trenton Porcelain Co. | 1-3/16" diameter; cap only | |
| R-107 |
  |
Triangle M | emb | Illinois Electric Porcelain Co. | 1-1/8" diameter | |
| R-36 |
  |
Triangle M / BULL DOG | r-e | Illinois Electric Porcelain Co. | unglazed; radially ribbed cap; captivated nail | |
| R-93 |
  |
Triangle M / X / BULL DOG | r-e | Illinois Electric Porcelain Co. | glazed; radially ribbed cap; captivated nail | |
| R-125 |
  |
Triangle M / BULL / E / DOG | r-e | Illinois Electric Porcelain Co. | 'unglazed where r-e BULL DOG; radially ribbed cap | |
| R-53 |
|
Triangle M / PAT FEB 3 1920 // BULL - DOG | r-e / emb | Illinois Electric Porcelain Co. | 1-3/16" diameter | |
| R-40 |
|
Triangle M / PAT FEB 3 1920 // BULL DOG 98 | r-e / emb | 1,329,656 | Illinois Electric Porcelain Co. | radially ribbed cap |
| R-13 |
   |
Triangle M PATD FEB 3 1920 // BULL DOG | r-e | 1,329,656 | Illinois Electric Porcelain Co. | captivated nail; radial ridges under cap |
| R-59 |
|
U / 5 1/2 | r-e | 1-1/8" diameter | ||
| R-135 |
  |
WEBER | r-e | 917,207 | Weber Electric Co. | 1" diameter; offset hole |
| R-10 |
|
WEDGE / C. P. CO. PATD; (top of bottom part: PAT. APR. 27, 1909) | r-e | 919,386 | Cook Pottery Co. | bottom has 1 groove and 3 recessed slots underneath; radial ridges under cap; patents 919,386 and 1,218,181 |
| R-129 |
   |
WEDGE / C. P. CO. PATD | r-e | 919,386 | Cook Pottery Co. | bottom has 2 grooves and 3 recessed slots underneath; radial ridges under cap; patents 919,386 and 1,218,181 |
| R-150 |
 |
WEDGE / C. P. CO. PATD | r-e | 919,386 | Cook Pottery Co. | bottom has short extended inner skirt underneath; radial ridges under cap; patents 919,386 and 1,218,181; glazed black |
| R-109 (don't have) |
   |
WEDGE // PATENTED (bottom) | r-e/emb | 919,386 | Cook Pottery Co. | Probably made before R-10 and R-129; patent 919,386 |
| R-72 |
|
WES co / 5 1/2 / U | emb | 1-1/8" diameter | ||
| R-65 |
|
W P CO | emb | Wisconsin Porcelain Co. | 1-3/16" diameter | |
| R-111 (don't have) |
  |
WP 5 1/2 / UL | r-e | Wisconsin Porcelain Co. | concentric ribbed cap | |
| R-91 |
 |
WS / U S | emb | 1-1/8" diameter, unglazed | ||
| R-04 |
  |
W. T. CO. PAT'D JULY 23 1919 | emb | 1,311,483 | Wheeling Tile Co. | radially ribbed cap |
| R-64 |
  |
W. T. CO. PAT'D APR 26 1921 | emb | 1,376,307 | Wheeling Tile Co. | 1-3/16" diameter; radially ribbed cap |
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