A method of manufacturing a handheld computing device that includes an electronic component assembly including at least one user interface component and an enclosure. The enclosure is a tube that is extruded. The extruded tube defines an internal lumen between open ends, and has a substantially uniform cross section along a longitudinal axis thereof. The extruded tube includes a front face, a back face, side portions connecting the front face and the back face, at least one access opening provided on the front face, and a pair of guide rails formed in the lumen along the side portions in parallel with the longitudinal axis. The electronic component assembly is slidably inserted into the lumen along the guide rails. The guide rails support the electronic component assembly and provide a reference surface for positioning the electronic component assembly relative to the front face such that the user interface is placed right behind the access opening to provide user access therethrough.