Interesting...the summit brand instructions pdf says nothing about a slit (as expected) lap joint while another does mention a slit outer pipe. Trying to find it. Yes, a clamp manufacturer site says "lap joint--- ID/OD slip fit connection preferably with compression slit(s)".....so it could clamp using od onto id as well as just a common clamping of both sides. Sounds good to me. Anything beats those cheap rigid U strap style clamps that ruin the pipe.