Putting Things in the Ass for My Boyfriend

my boyfriend has tried many different kinds of selfbondage, but he never dares to insert things in his bottom!? I want to help him, but he refuses. What can I do? He thinks it will hurt him, but he really wants to try…Is there an easy way for beginners? Guys, can you help me? I found that putting things into a woman’s bottom is easier than a man’s.