a tool for using in aligning , fastening , supporting , and sealing adjacent sections of a mandrel having a curved outer surface is provided . this tool has a t - shaped cross section and includes a leg section that has a composite sheet extending through the middle of it and a top section that is integral with said leg section . the top section has a pair of grooves therein spaced apart from each other along the length of the tool where o - ring means fits in the grooves and seals the adjacent section of the mandrel gas tight .