Heavy Duty Direct Burial Ground Clamps for Rebar for 2.5-4in. Pipe Heavy duty direct burial ground clamps for rebar are used to connect bare copper wire to copper water pipe, ground rods and rebar for bonding. Assembled with copper alloy screws and UL Listed for direct burial in earth and concrete. Can accommodate ground wires up to 2 AWG. cULus Listed 467 Grounding and Bonding.