Abstract: There are disclosed rams for blowout preventers having blades on their inner ends in position to shear or sever a pipe or other object extending within the bore of the preventer housing as the rams are moved within guideways intersecting the bore from outer positions, in which the bore is open, to inner positions in which shear edges on opposed faces of the blades pass over another. The rams also carry packing for sealing with respect to the guideways in which they move as well as with respect to one another to close off the bore following shearing of the object.