I am trying to remember the name of a movie I saw in my younger years. I think it was a post-apoc sci/fi flick, but the only thing I remember is a scene when the hero/heros are making camp for the night in this building and are later woken by these ugly, fat and slimy humanoids popping out of the wall and attacking them. It looks like they are riding on a shute.

Please help if you can