UU Plastic Housings consist of two "U" formed plastic pieces. One of which has a tongue and the other has a groove milled into the material. Insert the tongue into groove and the enclosure snaps together. In addition, if there is enough "land" on the edge of a PCB, a PCB may be able to be snapped into a milled board groove. The use of the board groove removes the need for mounting standoffs. Mounting ears are optional.
This style also works great for smaller plastic housings and Raspberry Pi mini computers. We can make many different accommodations based on what your custom Raspberry Pi enclosure or Raspberry Pi 3 enclosure requires.