A mortar board is used as a bed or slab upon which mortar can be mixed or placed. It is made of four or five 9-inch boards each 3 or 4 feet long, and framed together on the under side. Its use is to prevent the new mortar coming in contact with the scaffold boards.

Tarpaulins are made of strong canvas, and are thoroughly imbued with tar or an equivalent composition to render them waterproof.

Grindstones are various according to the kinds of edge-tools to be sharpened, and vary in size from 10 by 1 1/2 inches to 70 by 12 inches. They are usually fitted with handle and foot treadle and spindle, and mounted on friction roller.

Mortar Boards 248

Fig. 216.

The stones may be of " Newcastle" stone or " Free grit." Side plates may be attached.