>For example a cell phone, you could build it with an aluminum back with small phillips screws instead of glued back. Open the phone up with a standard screw dr

>For example a cell phone, you could build it with an aluminum back with small phillips screws instead of glued back. Open the phone up with a standard screw driver and you will be able to replace the battery, main board and screen yourself. You don't need screws on the back. The Samsung Galaxy phones (particularly the S4, S5, and S7) do just fine with a snap-on back. The S5 in particular is nicely water-resistant, even though the back is snap-on and can be removed with your fingernail. I guess an aluminum back might be nice for ruggedness, but as Samsung shows, screws aren't really necessary. It's entirely possible to design something made of inexpensive plastic that works great, is waterproof, and just snaps together, and can be opened and re-snapped together countless times without breakage.