If you have a door that won't stay open, this is the thing for you. It's a simple, quick print which mounts on the back of a door with double stick tape and/or a screw. It grips a doorstop with enough friction to hold the door open, but still can be easily pulled shut.
Mine works with a spring type doorstop, but it should work with other types by simply scaling it as needed.

http://youtu.be/SVnEKdk9svU

I printed mine on my DaVinci 1.0 at the Good setting.
Scale it as needed for a firm friction fit to your doorstop.
For perfect alignment, apply a piece of double stick foam to the flat side (I used a small Command Strip). Snap it on your doorstop and open the door against the holder. The holder will transfer to the door in just the right place. Optionally, add a small flathead screw.
Easy peasy.