THE TEE-SQUARE.
This is an instrument in the form of a letter T, as shown in the [figures 149 and 150]; the two parts are known as stock and blade; the horizontal part of the letter (T) is the stock, and the vertical part the blade—hence the name, T-square; to form the square, the two parts are joined together in such a way as to make them exactly at right angles to each other; the stock, which is applied to the working edge of the drawing board, being about one-third the length of the blade, and about three times its thickness.
Figs. 149 and 150.
To be perfect in construction, a tee-square should be as light as is consistent with its necessary strength and stiffness of parts; it should be made of suitable material easily manufactured, put together, and repaired, and withal as truly correct as is possible to be made. Such a square is represented in [fig. 148]; it has a taper blade, which is generally about double the width where secured to the stock as it is at the end.
Figs. 151 and 152.
The manner in which the stock is united to the blade determines its adaptability or otherwise to the use made of it; in some the stock is rectangular in section, and the blade mortised into it; in others the blade is dovetailed and let into the stock for the whole of its thickness.