Ask why? If he's afraid of heights, set a low stand, even in your yard, say 4 feet up. Then slowly move it up as he gets comfortable. Rig up a rope from above the stand hanging down and use a prussic knot from his harness to the rope as he climbs up. This should give him some security for fear of falling.

Climb up one step behind him. I did this with my 13 year old this fall to get him up his first one, also to help hook into the harness up there. With you one step below, his legs are actually inside you to give him "support"

If all else fails, millions of deer have been shot from the ground, it works!