There are timber braces fitted across the corners which are bolted through the outside timbers to brace the frame against a diamond tendency when moving the derrick. There is considerable strain when passing over uneven ground. It is better to make the frame so solid that it cannot get out of square. The mast is a stick of timber 8 inches square and 20 or 24 feet long. This mast is securely fastened solid to the center of the frame by having the bottom end mortised into the center cross timber at the middle and it is braced solid and held perpendicular to the framework by 4" x 4" wooden braces at the corners. These braces are notched at the top ends to fit the corners of the mast and are beveled at the bottom ends to fit flat on top of the timbers. They are held in place by bolts and by strap iron or band iron bands. These bands are drilled with holes and are spiked through into the timbers with four-inch or five-inch wire nails. Holes are drilled through the band iron the right size and at the proper places for the nails. The mast is made round at the top and is fitted with a heavy welded iron ring or band to prevent splitting. The boom is usually about 30 feet long. Farmers prefer a round pole when they can get it. It is attached to the top of the mast by an iron stirrup made by a blacksmith. This stirrup is made to fit loosely half way around the boom one-third of the way up from the big end, which makes the small end of the boom project 20 feet out from the upper end of the mast. The iron stirrup is made heavy and strong. It has a round iron gudgeon 1-1/2" in diameter that reaches down into the top of the mast about 18 inches. The shoulder of the stirrup is supported by a square, flat iron plate which rests on and covers the top of the mast and has the corners turned down. It is made large to shed water and protect the top of the mast. This plate has a hole one and a half inches in diameter in the center through which the stirrup gudgeon passes as it enters the top of the mast. A farm chain, or logging chain, is fastened to the large end of the boom by passing the chain around the boom and engaging the round hook. The grab hook end of the chain is passed around the timber below and is hooked back to give it the right length, which doubles the part of the chain within reach of the man in charge. This double end of the chain is lengthened or shortened to elevate the outer end of the boom to fit the stack. The small outer end of the boom is thus raised as the stack goes up. [Illustration: Figure 154.--Hay Rope Pulleys. The housing of the pulley to the left prevents the rope from running off the sheaves.]