I printed this cool mini catapult by ATECH: http://www.thingiverse.com/thing:438870 The result was awesome, the catapult shoots great distances with good precision, however I noticed that the thin base tends to fold up when the rubber bands are fully stretched (to achieve greater distances). I decided to add two supports on the side of the base, and I included diagonal slots on the bottom part of the rails to make room for the rubber bands, so that the whole catapult is flat on the ground. UPDATE: I designed an improved version (files marked with v2), with the sliding slots terminated on both sides so that the supports would not slide backwards after shooting. I also deepened the slots for the rubber bands, so that the catapult will rest flat on the undelying surface even if larger rubber bands re used. The catapult in the picture features my other addition, a triggering mechanism: http://www.thingiverse.com/thing:865653I printed this with 0.2mm layers, in PLA. Once printed, simply slide the two rails on the sides of the base and under the rubber bands that go round the sides, making sure the diagonal slots stay on the bottom of the catapult. There's no need to disassemble the catapult to mount the supports,