I bought a great picture but got no free space for it at any wall.. But free space on a sloped wall... So i needed a solution to attach the picture to a sloping wall. Here's what came to mind. A pin and a mounted gap where the pin can slide in and hold. Keep it simple and stupid. Well.. The only stupid thing is that it's not that easy to attach.
That's the way i managed it:
Mount all screws with the pins to one side (i used the frameside, wall side sould worked also) and one slider to the other side with the screw. Then mount the slider on the screws (some one-sided tape in the slot help to stay in position) with some double-sided tape on the mounting (wall) side. Make sure that all open slots are on one direction. Inside the one holder and press the others by pushing the picture at the wall. Then unslide all holders by shoving the pins out of the slides. Now you can fasten the slider with screws. Finished!
My screws got a upper diameter of 9 mm and a lower diameter of 4.5 mm. Shoud worked with smaler screws or scaled objects too.