Question
I want to install a zip line in my backyard for my granddaughters. Can I install eye bolt anchors to my crimson maple and my ash tree without damaging the trees and if so, what protection should I plan to use to protect the tree after I drill in the anchore.

Answer
Use steel bolts and run them through the tree trunk and fastened with a large washer. Tighten the bolt so it will not move or wiggle. The tree will form cells around the bolt and keep out decay fungi. Make the hole for the eye bolt just large enough for the diameter of the bolt to prevent the bolt from moving in the tree. Use eye-bolts with round washers and a nut. Pre-drill eye-bolt holes one-sixteenth of an inch larger than the eye-bolts shafts. Drilling requires a special extra-long bit for big branches. Do not use any type of lubrication on the bolts and do not attempt to seal the edges of the drilled hole. Tighten the nut firmly against the washer on the back side. The washer should be seated into the bark only as far as the surface of the wood. Do not scrap pieces of the bark off the tree larger than the bolt washer. Minimize the surface area of any damage.

Once the eye bolt is in place do nor remove them. You may get some sap form the maple but this will stop as the wound heals.