A pipe clamp (10, 210) comprising: a band (28, 228) extending circumferentially from a first end to a second end; a tightening mechanism connected to said band near said first and second ends, said tightening mechanism including at least one fastener to bring said first and second ends toward each other to tighten said band; a split sleeve (14, 214) located radially inside of said band, said split sleeve extending axially from a first side to a second side and extending circumferentially from a first circumferential end (70, 270) to a second circumferential end (72, 272), said split sleeve having at least one channel (82, 281, 283) located between said first and second sides and extending between said first and second circumferential ends, said split sleeve including at least one tongue-and-groove joint (88, 90, 92, 291, 293, 295, 297), said tongue (98, 116, 298, 316) being located at said first circumferential end and said groove (100, 118, 300, 318) being located at said second circumferential end confronting said tongue; and at least one gasket (12, 211, 213) located radially inside of said split sleeve and received in said channel; said tongue having a side edge (106, 108, 126, 128, 326, 328) and said groove having a side edge (112, 114, 130, 132, 332, 330) that confronts said side edge of said tongue at one or more points along their length during penetration of said tongue into said groove such that said tongue and said groove have areas of spaced separation between their confronting side edges when said band is fully tightened about a pair of abutting pipe ends (20, 24); wherein, upon tightening of said band and penetration of said tongue into said groove, said gasket is wedged into at least some of said areas of spaced separation between said side edges of said tongue and groove, characterized by said gasket being wedged into at least some of said areas of spaced separation between said side edges of said tongue and groove forming a seal therebetween, wherein said gasket is a split gasket extending circumferentially from a first circumferential end to a second circumferential end, said first circumferential end located at said tongue and, when not tightened and not penetrated, said first circumferential end has a circumferential overhang portion (152, 352) overhanging a free end of said tongue, said second circumferential end located at said groove and, when not tightened and not penetrated, said second circumferential end has a circumferential overhang portion (158, 358) overhanging a bottom edge (134, 334) of said groove. a band (28, 228) extending circumferentially from a first end to a second end; a tightening mechanism connected to said band near said first and second ends, said tightening mechanism including at least one fastener to bring said first and second ends toward each other to tighten said band; a split sleeve (14, 214) located radially inside of said band, said split sleeve extending axially from a first side to a second side and extending circumferentially from a first circumferential end (70, 270) to a second circumferential end (72, 272), said split sleeve having at least one channel (82, 281, 283) located between said first and second sides and extending between said first and second circumferential ends, said split sleeve including at least one tongue-and-groove joint (88, 90, 92, 291, 293, 295, 297), said tongue (98, 116, 298, 316) being located at said first circumferential end and said groove (100, 118, 300, 318) being located at said second circumferential end confronting said tongue; and at least one gasket (12, 211, 213) located radially inside of said split sleeve and received in said channel; said tongue having a side edge (106, 108, 126, 128, 326, 328) and said groove having a side edge (112, 114, 130, 132, 332, 330) that confronts said side edge of said tongue at one or more points along their length during penetration of said tongue into said groove such that said tongue and said groove have areas of spaced separation between their confronting side edges when said band is fully tightened about a pair of abutting pipe ends (20, 24); wherein, upon tightening of said band and penetration of said tongue into said groove, said gasket is wedged into at least some of said areas of spaced separation between said side edges of said tongue and groove, characterized by said gasket being wedged into at least some of said areas of spaced separation between said side edges of said tongue and groove forming a seal therebetween, wherein said gasket is a split gasket extending circumferentially from a first circumferential end to a second circumferential end, said first circumferential end located at said tongue and, when not tightened and not penetrated, said first circumferential end has a circumferential overhang portion (152, 352) overhanging a free end of said tongue, said second circumferential end located at said groove and, when not tightened and not penetrated, said second circumferential end has a circumferential overhang portion (158, 358) overhanging a bottom edge (134, 334) of said groove.