A hydraulic hammer may include a power cell adapted to reciprocally drive a piston along an axis. The piston may, in turn, drive a hammer tool having a first end juxtaposed against the piston for accommodating cyclic impacts by the piston. While the first end of the hammer tool may be contained within a housing, the other end may extend from the housing for impacting rock, for example. The power cell and housing are axially secured together by a plurality of tie rods and nuts secured to ends of the tie rods, and the housing may include exterior pockets for accommodating the nuts. Each nut may have a circular exterior surface, and each nut pocket may have a generally elliptical interior surface, such that the exterior surface of each nut may be configured to engage at least two spaced apart areas of a corresponding interior surface of each nut pocket.