190 PRACTICAL TREE REPAIR 



the spreading of the sides of the cavity is accom- 

 modated by the surplus metal. 



When the incision is completed and everything 

 is ready for the tin, proceed as follows: Make 

 a paper pattern of the whole opening, if it is 

 small, or of the lowest section if it is large, mak- 

 ing sure that the paper is not stretched or folded 

 in a way the metal itself is not capable of. Lay 

 the pattern on the metal, scratch with a nail the 

 line of its edge, and cut out the shape. Fit the 

 metal over the opening, trimming off the edge 

 here and there if necessary to make a perfect fit. 

 Paint the back of the tin with tar or paint. Paint 

 the edges of the opening, the strip of wood, that 

 is, to which the tin will be nailed, with heavy liquid 

 asphalt. Now fit the tin into place and tack it 

 there with nails four or five inches apart. If the 

 metal is heavy it is a good idea to punch holes 

 around its outer edge with a small punch or a 

 sharpened spike. The nails must be very near 

 together an inch or even as little as half an 

 inch apart. Where circumstances permit it, stag- 

 ger the nails, putting some farther from the edge 

 of the tin than others. After nailing it is a 

 good idea to go over the edge of the metal with 

 some such tool as a dull cold-chisel, pounding the 

 edge into the wood a little so that the growing 

 callus cannot by any chance get under it. 



It is hardly necessary to say that this work is 



