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House wiring split knobs were popular in the early part of the 20th century.  Manufacturers patented numerous "improvements" and a large number of companies entered the market to meet the huge need to electrify homes.

Terminology

There are many terms for these types of insulators:

• Nail knobs.  
• Screw knobs
• Split knobs
• Standard porcelain
  

In describing the features of a nail knob, there are several terms used:

• Diamond waffle.  A criss-crossing pattern of raised porcelain designed to grip the wire generally found on the cap of a nail knob rather than on the base.  The intersecting ridges of porcelain are at a 45 degree angle, creating a diamond shape between the ribs.
• Off-centered hole.  Rather than the nail hole going through the center of the insulator, one patent was issued for the nail hole to be off-centered.
  
• Radiating ribs.  Raised ridges of porcelain that are oriented along the diameter of the nail knob, generally found on the cap of a knob.
• Square waffle.  A criss-crossing pattern of raised porcelain designed to grip the wire and generally found on the cap of a nail knob rather than on the base.  The intersecting ridges of porcelain are at a 90 degree angle, creating a square shape between the ribs.
• Waffle.  A criss-crossing pattern of raised porcelain designed to grip the wire.  The intersecting ridges of porcelain can be at various angles, creating different shapes between the ribs (see, for example, the description of diamond waffle and square waffle)
  

Name	Marking	Cap type	Base type	Notes
Brunt	(embossed in circle on top cap) BRUNT	2 wire grooves with 5 ribs, recessed rectangle with convex short sides around nail hole	2 wire grooves, 5 ribs, upward extending center in the shape of a rectangle with convex sides on the short side of the rectangle	White
Bulldog	(embossed in circle on top cap) BULL / DOG / W	Radiating ribs	2 wire grooves with four gripping ribs	White
C	(r-e on top) C	Radiating ribs	2 wire grooves with 8 ribs, upward extending center	White
CCE	(incuse on top) CCE [could also be GCE or CCE] // (r-e on other side of nail hole) D [Tod lists it as CCE but I think it might stand for Canadian General Electric or CGE]	4 wire grooves forming a square, 3 ribs, extended nail hole	2 pairs of wire grooves at 90 degrees, 3 ribs in wire groove, recess around nail hole	White
HP (Hamilton Porcelain)	(embossed on cap) [HP logo in which P is part of H]	Radiating ribs with bisecting ring	??	White
Jiffy	(embossed in cirlce on top cap) N-T-P-CO.- / JIFFY- / 10 [the zero is small like a degree symbol]	1 ring	2 wire grooves with ribs	White
Macomb	(embossed in circle on top cap) MACOMB	2 wire grooves with 12 ribs. Wedge parallel to wire grooves to keep cap from spinning	2 wire grooves with 12 ribs.  Valley parallel to wire grooves to keep cap from spinning	White
Monowatt	(embossed in circle on top cap) MONOWATT	2 rings	2 wire grooves with four  gripping ribs	White
Nailit	(r-e in circle on top cap) NAILIT // PAT. 2.3.1920	Radiating ribs	2 wire grooves with gripping ribs	White
No Name		Square waffle	2 wire grooves with five gripping ribs	White
No Name		2 wire grooves with 6 ribs, pyramid shaped indentation on one side of nail hole, pyramid shaped protrusion on other side of nail hole. Pyramids are parallel to wire grooves	[Probably the same as the cap]	White
Patent	(embossed on top in circle) PATD FEB-3-1920	Diamond waffle	??	White
S & S (Smith & Stone, Canada)	(r-e on top) S & S	2 rings, extended center to prevent flashover to nail	??	White
Unknown			Two pairs of 2 wire grooves, 3 ribs per groove, upwarding extending circular part around nail hole	White

   
This page created December 16, 2004.