How to fuse/weld/combine 2 "tunnles" in scuplting Im fairly new to blender probably only a month 1/2 or so in.
I thought doing a skull tonight would be a good practice sculpt but Iv run into an issue in that I cant connect these "tunnels" (not sure what the exact terminology would be) nor can i seem to find a solution via searching.

The closest thing iv come up with is a Boolean union but they are part of the same mesh or do all the bits separately then union them...im at a loss.
Fastest way to solve this is:

Go to edit mode. Select the areas oposing each other (probably with C - circle selection).

Run Edge - bridge edge loops. 

I assume you are using Dyntopo - dynamic topology, so then you can return to sculpt mode, and with dyntopo on, you can add resolution and smooth this area.