I am trying to determine the best way to attach trail signs to trees in the woods.
The problem with trees is that they grow. If you firmly embed a nail in the wood, the tree will eventually grow around the nail head. When we put up small plastic trail markers (what we use a blazes), we deliberately leave a ½ inch or so gap between the nail head and the marker. Put another way, we don't bang the nail in all the way. This gives the marker room to slide along the nail, instead of the growing tree pushing all around behind the nail head, and eventually buckling and cracking the plastic marker.
I am now going to put up some aluminum signs that will last much longer than the plastic trail markers. A tree could grow multiple inches over the expected life of the sign. What I'd like is a way to mount the sign so that it stays on the outside, moving with the growth of the tree instead of getting swallowed up by it.
It seems that just the right diameter and length of nail might do it. You want the sign to be held, but the nail be able so slide out as the tree grows and pushes against the sign. What diameter and depth might that be? What studies are there that have looked into this? What experience do you have with this?