[Illustration: Figure 17.--Try-Square With Six-Inch Blade. Wood, brass and steel are the proper materials for a try-square. A double marking gauge for scribing mortises is also shown.] Steel squares differ in the measuring marks, but the kind to buy has one side spaced to sixteenths and the other side to tenths or twelfths. The sixteenth interest farmers generally, so that special attention should be given this side of the square. The lumber rule on some squares is useful, but the brace rules and mitre calculations are not likely to interest farmers. Screw-drivers should be mostly strong and heavy for farm work. Three sizes of handled screw-drivers of different lengths and sizes, also two or three brace bit screw-drivers are needed. One or two bits may be broken or twisted so the assortment is sometimes exhausted before the screw is started. [Illustration: Figure 18.--Heavy Hand Axe for Use on the Shop Chopping Block. A beet topping knife is shown also.] [Illustration: Figure 19.--Heavy Screwdriver. The strongest and cheapest screw-driver is made from a single bar of steel. The wooden handle is made in two parts and riveted as shown.] Pinch bars and claw bars are very useful in a farm tool kit. Farm mechanical work consists principally in repairing implements, machinery, fences and buildings. Always a worn or broken part must be removed before the repair can be made. A pinch bar twenty-four inches long, Figure 21, with a cold chisel end, and another bar eighteen inches long with a crooked claw end, Figure 22, for pulling nails and spikes comes in very handy. These two bars should be made of the best octagon steel, seven-eighths of an inch in diameter. [Illustration: Figure 20.--(1) Ratchet Screwdriver. It does rapid work and will last a generation if carefully used. (2) Auger-Bit of the Side Cutter Type. A full set is needed. They are not for boring into old wood. Running once against a nail ruins one of these bits.] [Illustration: Figure 21.--Handspike. A wooden handspike or pry is about seven feet long by 3 inches thick at the prying end. In the North it is usually made from a hickory or an ironwood or a dogwood sapling. The bark is removed and the handle is worked round and smooth on the shave horse. It is better to cut the poles in the winter when the sap is in the roots. After the handspikes are finished they should be covered deep with straw so they will season slowly to prevent checking.] [Illustration: Figure 22.--Wrecking Bar for pulling nails and to pry broken parts from other wreckage.] [Illustration: Figure 23.--Carpenter's Level. For practical farm work the level should be 24" or 30" long. Wood is the most satisfactory material. The best levels are made up of different layers of wood glued together to prevent warping or twisting. For this reason a good level should be carefully laid away in a dry place immediately after using.]