126 PRACTICAL TREE REPAIR 



suited to the purpose. The number of bolts de- 

 pends upon the size of the tree, the thickness of 

 the sound wood, and the number and size of the 

 openings of the cavity. As the most common 

 function of the braces is to prevent the formation 

 of cracks around the filling, they are usually in- 

 serted as close to the mouth of the cavity as pos- 

 sible, reminding one of the stitches with which a 

 surgeon closes up a wound. It is not often that 

 the bolts need be closer together than eighteen 

 inches. The diameter of the bolts should be kept 

 down to the minimum of safety, not only to save on 

 the cost of the iron, but also to avoid making un- 

 necessarily large holes in the bark in inserting them. 

 Considering that the steel of which machine bolts 

 are made has a strength of fifty thousand pounds 

 to the square inch, it is evident that anything 

 larger than five-eighths bolts will not often be 

 needed. Bolts in trees give way, when they do, 

 by snapping off, or pulling out of, their heads. 

 When ordering special sizes and extra lengths from 

 the blacksmith the best way is to have both ends 

 of the bolt threaded. A nut can be set on one 

 end and can be considered as a head, or both nuts 

 can be used to tighten up the bolt. 



In case the slope of the bark toward the mouth 

 of the cavity is such that a large socket would have 

 to be cut in order to form level floors for the head 

 of the bolt and the nut, it is better to run them 



