It seems that unit blocks have their own lingo when referring to sizes and shapes. Here’s a chart to help you quickly navigate which shapes and sizes are available, and what to call them. The illustrations are courtesy of one of the best block makers in the business:

Wooden Unit Block Size and Shape Chart

Illustration	Name	Size (inches)
	1/2 Unit	1-3/8 X 2-3/4 X 2-3/4
	Unit	1-3/8 X 2-3/4 X 5-1/2
	Double Unit	1-3/8 X 2-3/4 X 11
	Quad Unit	1 3/8 X 2-3/4 X 22
	1/2 Pillar	1-3/8 X 1-3/8 X 2-3/4
	Pillar	1-3/8 X 1-3/8 X 5-1/2
	Double Pillar	1-3/8 X 1-3/8 X 11
	1/2 Column (1")	Round X 2-3/4
	Column	Round X 5-1/2
	Double Column	Round X 11
	Roman Arch	1-3/8 X 2-3/4 X 5-1/2
	1/2 Circle	1-3/8 X 2-3/4 Circle
	Small Triangle	1-3/8 X 2-3/4 Triangle
	Large Triangle	1-3/8 X 5-1/2 Triangle
	Double Triangle	1-3/8 X 11 Triangle
	Ramp	1-3/8 X 5-1/2 Ramp
	1/2 Basic Flat	11/16 X 2-3/4 X 2-3/4
	Flat	11/16 X 2-3/4 X 5-1/2
	Double Flat	11/16 X 2-3/4 X 11
	Quad Flat	11/16 X 2-3/4 X 22
	Roof Board	1/8 X 5-1/2 X 11
	Intersection	1-3/8 X 8-1/4 X 8-1/4
	Side Road	1-3/8 X 5-1/2 X 8-1/4
	1/4 Circle	1-3/8 X 2-3/4 Circle
	Large 1/2 Circle	1-3/8 X 2-3/4 X 5-1/2
	1/2 Circle Curve	1-3/8 X 5-1/2 X 5-1/2
	Circle Curve	1-3/8 X 5-1/2 X 11
	Small Switch	1-3/8 X 5-1/2 X 8-1/4
	Gothic Arch	1-3/8 X 11" x 8-1/4
	1/2 Gothic Arch	1-3/8 X 2-3/4 X 5-1/2
	Small Buttress	1-3/8 X 1-3/8 X 4-1/8
	Gothic Door	1-3/8 X 5-1/2 X 2-3/4
	1/2 Roman Arch	1-3/8 X 2-3/4 X 2-3/4
	Notched Half Unit	1-3/8 X 2-3/4 X 2-3/4