A manhole insert wherein gusset (58,60) and (62,64) or offset sections (142,144) and (146,148) anchor pins (94,96) or (158,160) that can be grappled with tools (not shown) to remove the insert. The bottom of the insert includes a conical frustum (40) and an inverted cone (48) or a panel that has a convex...http://www.google.es/patents/US5957618?utm_source=gb-gplus-sharePatente US5957618 - Manhole insert
