Pop-up and spinner rigs present a buoyant hookbait just off the bottom, where carp find it easily. On a spinner or ronnie rig the hook sits on a swivel and turns readily into a hold. These rigs suit hard bottoms and light debris.
A pop-up floats, so the rig needs a counterweight, usually tungsten putty or a small pop-up weight near the hook. Adjust it so the bait hovers a few centimetres above the bottom with the hook sitting at the right angle.
On a spinner rig the hook is attached to a rotating swivel, so it can turn freely in any direction. That makes the rig very efficient, and a stiff boom stops it from tangling.
Always test the rig in the margin before casting. When the bait sits correctly, you know the rig is working on the spot too. Swap the pop-up during long sessions, as a waterlogged bait loses its buoyancy.