Abstract: An apparatus and method for forming a housing assembly. The assembly comprises a first part with protrusions spaced along at least one surface which fit into through-holes in a second part and which may, when the parts are placed together, be peened such that the protrusions fill the through-holes and join the parts. The method comprises fabricating a first part with protrusions and a second part with through-holes, joining the parts together such that the protrusions mate with the through-holes, and peening the protrusions such that they fill the through-holes and join the parts.