i depicts a fuel cell stack 600 comprising fuel cell assemblies interposed between end plates 605 at this stage fuel cell stack 600 is not compressed but internal tension member 610 has been inserted through an opening which extends through the interior of fuel cell stack 600 and end plates 605 the opposite ends of tension member 610 protrude from end plates 605 diagram ii depicts spring plates 615 positioned next to each end plate in diagram iii collets 620 have been inserted into openings provided in spring plates 615 flanges on collets 620 are seated against spring plates 615 an opening in collet 620 is aligned with tension member 610 in the step illustrated by diagram iv an external compressive device 625 pushes against the compression assembly in the longitudinal direction of the tension member as indicated by arrows in diagram iv external compressive device 625 compresses fuel cell stack 600 causing tension member 610 to protrude through collets 620 with reference to diagram v once fuel cell stack 600 is compressed member 630 of external compression device 625 continues to apply a linear compressive force in the longitudinal direction of the tension member to insert wedges 635 into respective gaps between collet 620 and tension member 610 wedges 635 are inserted until they fill the available gaps such that linear forces.