A rivet, including: at least one side wall extending from a first side of a sheet of material, formed from the same material as the sheet of material, and including respective inside surfaces; and a space at least partly enclosed by the respective inside surfaces. The space is open at a second side of the sheet of material. In one embodiment, the at least one side wall is cylindrical in shape. In another embodiment, the rivet includes an end wall formed of the same piece of material as the at least one side wall and defining one end of the space, the space is cylindrical in shape, the space has a first portion aligned with the sheet of material and a second portion partially defined by the end wall, and a diameter for the first portion is less than the diameter for the second portion.