Nail Knobs, Split Knobs
and Other House Wiring
Knob Insulators
page 1 of 5
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.
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
O = oval
S = square or rectangular
SR = square or rectangular reversible knob
/ = marking on opposite side
// = marking on bottom
| No. | MARKING | Marking Type | Patent | Company | Notes |
|---|---|---|---|---|---|
| Nail Knobs | |||||
| R-01 | MACOMB | emb | Illinois Electric Porcelain Co. | ||
| R-02 | BMOCAM (Macomb) | emb | Illinois Electric Porcelain Co. | matching V-grooves on cap and base | |
| R-03 | SUPERIOR / 5½ | emb | Superior Porcelain Co. | corrugated cap and ring outside; captivated nail | |
| R-04 | W. T. CO. PAT'D JULY 23 1919 | emb | 1,311,483 | Wheeling Tile Co. | radially ribbed cap |
| R-05 | P.P. INC. / ALLIGATOR | emb | Porcelain Products Inc. | captivated nail; corrugated under cap with raised ring around outside | |
| R-06 | N-N | cone top, cone recessed bottom; corrugated cap with raised ring around outside; captivated nail | |||
| R-07 | SPW / UL / 110 | r-e | Specialty Porcelain Works | concentric rings under cap; captivated nail | |
| R-08 | N-N | rounded top, cone recessed bottom | |||
| R-09 | N-N | rounded top, deep recessed bottom | |||
| R-10 | WEDGE / C. P. CO. PATD; (top of bottom part: PAT. APR. 27, 1909) | r-e | 1,218,181 | Cook Pottery Co. | 3-slot recessed bottom; radial ridges under cap; also patent 919,386 |
| R-11 | MONOWATT | emb | ?? | concentric ring under cap; captivated nail | |
| R-12 | FEDCO | emb | Federal Porcelain Co. | corrugated cap; captivated nail | |
| 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-14 | NAILIT / PAT APPD FOR | r-e | J. H. Parker & Son | radially ribbed cap; captivated nail | |
| R-15 | BRUNT / CINCH // BRUNT | emb | Brunt Porcelain Co. | radially ribbed cap; captivated nail | |
| R-16 | MACOMB | emb | Illinois Electric Porcelain Co. | ribbed channels in cap and base | |
| R-18 | BRUNT (backward N) | emb | 917,207 | Brunt Porcelain Co. | 1" diameter, nail hole offset; matching V-grooves |
| R-19 | SPW (inside a diamond) | emb | Specialty Porcelain Works | 3/4" diameter, unglazed | |
| R-27 | (illegible patent date) | emb | 907,251 | Colonial Sign & Insulator Co. | specimen found at Colonial |
| R-28 | N-N | 907,251 | Colonial Sign & Insulator Co. | ||
| R-30 | PATD - FEB - 3 - 1920 (circle) | emb | 1,329,656 | Illinois Electric Porcelain Co. | cap corrugated underneath; bottom unglazed; captivated nail |
| R-31 | GRIP IT / PAT. | r-e | J. H. Parker & Son | cap only | |
| R-32 | A. P. CO. G. E. CO. 9419 (circle) | emb | Anderson Porcelain Co. | cap only; 1-1/2" diameter | |
| R-35 | NAILIT / PAT FEB. 3, 1920 | emb | 1,329,656 | radially ribbed cap | |
| R-36 | Triangle M / BULL DOG | r-e | Illinois Electric Porcelain Co. | unglazed; radially ribbed cap; captivated nail | |
| R-37 | P.P. INC. / ALLIGATOR / 5½ | emb | Porcelain Products Inc. | captivated nail | |
| 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-39 | NAT. / READY / PAT / 2-3-20. | emb | 1,329,656 | National Electric Porcelain Co. | unglazed; radially ribbed cap; captivated nail |
| 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-41 | GEE PEE | emb | General Porcelain Co. | radially ribbed cap | |
| R-42 | FINDLAY / ALLIGATOR | emb | Findlay Electric Porcelain Co. | corrugated cap | |
| R-43 | G | emb | 917,207 | 1" diameter, nail hole offset; matching V-grooves on cap and base | |
| R-44 | D. P. Co. / EVER / READY (in circle) | r-e | Davidson Porcelain Co. | concentric rings under cap | |
| R-45 | T | emb | R. Thomas & Sons Co. | 1" diameter, nail hole offset; matching slot | |
| Round Split Knobs, Oval Split Knobs, Round Reversible Split Knobs | |||||
| R-20 | F // F | emb | 464,770 | Findlay Electric Porcelain Co. | 1-3/8" diameter, caming groove |
| R-21 | G. E. KNOB / PAT APLD FOR // 9352 | emb | General Electric Co. | 1-1/2" diameter | |
| R-22 | G. E. KNOB // CAT. 6580 | r-e | General Electric Co. | 2" diameter | |
| R-23 | P. P. Inc. | emb | 2" diameter; matching vertical groove on the side | ||
| R-24 | P. P. Inc. / 9420 // P. P. Inc. / 9420 | emb | 2" diameter; matching vertical groove on the side | ||
| R-25 | G. E. KNOB // CAT. 6580 | emb | General Electric Co. | 2" diameter | |
| R-46 | G. E. KNOB // E P | emb / r-e | General Electric Co. | 1-1/2" diameter | |
| R-47 | D. P. CO // 9419 | emb / r-e | Davidson Porcelain Co. | 1-1/2" diameter | |
| O-01 | N-N | Colonial Sign & Insulator Co. | similar to patent 806,588 | ||
| O-02 | T / PAT / 4803 / NO. 5½ | emb | 697,001 | R. Thomas & Sons Co. | reversible, oval; error date, should be 4-8-02 |
| O-03 | STAR // (embossed star) PAT DEC 5 05 | r-e / emb | 806,588 | Star Porcelain Co. | |
| RR-01 | .G. PAT APPD FOR (circle) | emb | 1-1/8" diameter; reversible | ||
| RR-02 | BUCKEYE REGD (circle) PATD 12-31-12 / F (outer circle) | emb | 1,048,850 | Findlay Electric Porcelain Co. | reversible, crossover knob |
| RR-03 | T P I / NO 1 / T / PAT / APR / 803 | emb | 697,001 | R. Thomas & Sons Co. | 1-3/8" diameter, reversible, error date, should be 4-8-02 |
| RR-04 | T / PATD 7-20 / 1915 | emb | 1,147,498 | Trenton Porcelain Co. | 1-1/8" diameter; reversible |
| RR-05 | PAT. / APP.D. / FOR / G. (in circle, G inside circle) | emb | 1-1/8" diameter; reversible | ||
| RR-06 | F / PATD / 12-31 / 12 (in circle) | emb | 1,048,850 | Findlay Electric Porcelain Co. | 1-1/8" diameter; reversible |
| RR-07 | F / PATD / 12-31 / 12 (in circle) | emb | 1,048,850 | Findlay Electric Porcelain Co. | 1-1/4" diameter; reversible, crossover knob; error date 12-13 instead of 12-31 |
| RR-08 | T P I / NO 2 / THOMAS / PAT / APR / 8 03 | emb | 697,001 | R. Thomas & Sons Co. | 1-3/4" diameter; reversible |
| Square Reversible Split Knobs, Misc. Knobs, and Square Knobs | |||||
| SR-01 | U S / PATD / 2408 / 51611 | emb | 878,302 | US Electric Porcelain Co. | reversible |
| SR-02 | Triangle M / PAT'D / FEB 9 / 1915 | emb | 1,127,776 | Illinois Electric Porcelain Co. | reversible |
| SR-03 | U S / PAT'D (on short end) | emb | 878,302 | US Electric Porcelain Co. | reversible |
| SR-04 | U S / PAT'D (on long end) | emb | 878,302 | US Electric Porcelain Co. | reversible |
| R-17 | IDEAL // PATENTED / 5 28 07 | emb/r-e | 855,208 | Star Porcelain Co. | |
| R-26 | N-N | 965,723 | Paragon Electric Co. | ball fits on top of the base | |
| R-29 | PATENTED MAY 13 1902 (circle on bottom) | r-e | 699,761 | ||
| R-33 | PAT'D / JULY / 19 - 92 (on side) | emb | 479,134 | Conover patent | |
| R-34 | POLK / PAT'D MCH 10 | emb | 724,329 | three flanges on top for tying wire around the knob; saw-toothed bottom edge prevents turning | |
| S-01 | S-H Co. / No. 1 // A. P. C. L. / Pat. / Mar. 1, '04 | emb | 753,399 | Snyder-Hunt Co. | |
| S-02 | S-H Co. / No. 1 // MACOMB / PAT / MAR-1-04 | r-e | 753,399 | Illinois Electric Porcelain Co. | Snyder-Hunt Co. |
| S-03 | MACOMB. / PAT. / MAR-1-04 // S-H. co. / No. 1. | r-e | 753,399 | Illinois Electric Porcelain Co. | Snyder-Hunt Co. |
| S-04 | S H co. / no 1. // MACOMB. / PAT. / MAR-1-04 | r-e | 753,399 | Illinois Electric Porcelain Co. | Snyder-Hunt Co. |
| S-05 | Triangle M / PARALLEL / KNOB / PAT. APPL. FOR // E. L. KLINGEL / ST. PAUL | emb / r-e | 2,307,277 | Illinois Electric Porcelain Co. |
