Merging two drawing while keeping two separate layers

Hi there my names josh, I’m very new to animating and I’ve run into a problem that i hope you can help me with…

I am trying to make an arm with two separate layers (upper arm and lower arm). The problem is the two lines that
overlap do not merge.The only way i can merge them is by making the two layers into one layer, which isn’t what I’m
trying to do.

So is the a way to merge two drawings while keeping the two separate layers?
The reason i need them to be two separate layers, is so that i can animate both
parts of the arm individually.


Watch this video on how to use auto patch to do seamless merge joints for hands/legs/body/etc