These attachments fit combination square blades 1"
(25mm) wide and permit attaching rules, blades or thin
steel try squares, up to 1" (25mm) wide, at right angles to
the blade of the square for laying out key seats, centers,
scribing horizontal lines, and measuring diameters.
Available in two sizes listed below. Both sizes can also be
used with 289C Height and Depth Gage Attachment.