A method for assembling and sealing a reusable electrical surgical instrument, comprising: providing at least two body shells (10,110) of an instrument, each body shell having a side wall (20,120) about the perimeter thereof, said side wall having an interior surface (22,122), and exterior surface (24,124), and at least one joining surface (26,126) defined between the interior surface and the exterior surface, where a pair of mutual joining surfaces is defined by the joining surface of one body shell that is configured to mate with the joining surface of a second body shell, at least one joining surface of the pair of mutual joining surfaces having a runner system surrounding the perimeter substantially near the edge, the runner system having an inlet port, an outlet port, a principal section extending around said joining surface from the inlet port to the outlet port, and a bridge section connecting the inlet port and the outlet port across the portion of the perimeter of the joining surface that is not surrounded by the principal section; aligning the pair of mutual joining surfaces (26,126); securing the body shells (20,120) in position relative to each other; inserting an injection device into the inlet port past the bridge section; injecting an elastomer material from the injection device through the inlet port into the principal section of the runner until the elastomer material exits from the outlet port; removing the injection device from the inlet port while continuing to inject elastomer material from the injection device; and curing the elastomer material forming a seal along the pair of mutual joining surfaces (26,126). providing at least two body shells (10,110) of an instrument, each body shell having a side wall (20,120) about the perimeter thereof, said side wall having an interior surface (22,122), and exterior surface (24,124), and at least one joining surface (26,126) defined between the interior surface and the exterior surface, where a pair of mutual joining surfaces is defined by the joining surface of one body shell that is configured to mate with the joining surface of a second body shell, at least one joining surface of the pair of mutual joining surfaces having a runner system surrounding the perimeter substantially near the edge, the runner system having an inlet port, an outlet port, a principal section extending around said joining surface from the inlet port to the outlet port, and a bridge section connecting the inlet port and the outlet port across the portion of the perimeter of the joining surface that is not surrounded by the principal section; aligning the pair of mutual joining surfaces (26,126); securing the body shells (20,120) in position relative to each other; inserting an injection device into the inlet port past the bridge section; injecting an elastomer material from the injection device through the inlet port into the principal section of the runner until the elastomer material exits from the outlet port; removing the injection device from the inlet port while continuing to inject elastomer material from the injection device; and curing the elastomer material forming a seal along the pair of mutual joining surfaces (26,126).