I have an old mandolin that I hung on the wall very simply , just tied a loop of a twisted cord, encircled the upper neck and then pulled the remainder up between the pegs at the back and put the end over a picture hook. Very secure but easily removed. Doesn't damage the old mandolin, costs next to nothing for an old piece of plaited cord or rope, you don't need anything fancy , the more natural looking the better. It does look nice on the wall, gets the attention of musos who would like to take it down and try it out, too.