These are general blocks for the construction of a: http://en.wikipedia.org/wiki/Block_and_tackle Among other options you can choose the number of sheaves the blocks hold. DO NOT USE THIS TO SECURE LIFE OR OBJECTS OF HIGH VALUE ! THIS IS A FREE MODEL THE ENTIRE RISK OF USING THIS OBJECT IS WITH YOU I AM NOT REPONSIBLE FOR ANY DAMAGE ARISING OUT OF THE USE OF THIS OBJECT When using these you'll probably need to bind some knots: mid-rope-loop: http://en.wikipedia.org/wiki/Butterfly_loop non tightening loop: http://en.wikipedia.org/wiki/Bowline self tightening loop: http://en.wikipedia.org/wiki/Double_overhand_noose end knot: http://en.wikipedia.org/wiki/Figure-eight_knot keep rope tidy: http://de.wikibooks.org/wiki/Klettern/_Seiltransport (de Seilpuppe -> en ???) non tightening but adjustable loop: http://en.wikipedia.org/wiki/Blake%27s_hitch bindable under high tension: http://en.wikipedia.org/wiki/Round_turn_and_two_half-hitches The single and double sheave blocks with otherwise default settings are for rope with diameter of 4mm and M6 Bolts. With these you can make: 2 x advantage: Gun tackle 3 x advantage: Luff tackle 4 x advantage: Double tackle I've succesfully tested a Luff tackle with a load reduction from 15 to 5 kg To reproduce my setup you'll need one dual and one single sheave block. First assemble the blocks. Then put the single-sheave-blocks eyelet over one end A of the rope. With the ropes end A bind a self tightening loop around the load. Near the loop bind the sigle-sheave-blocks eyelet into a butterfly loop. Thread the ropes far end B through one of the sheaves of the double-sheave-block. Keep the block some distance away. Go back and thread B through the single-sheave-blocks sheave. Finally thread B through the second sheave of the double block. Try to keep everything untangled. Bind a stopper eight knot in the end of the rope to prevent it from slipping out. Use two bowline or self tightening knots to mount the eyelet of the double block to your support structure. Finished! Now you can start pulling. When the load is in place tie a blakes hitch around one of the tensioned ropes to secure it. Print with the layers perpendicular to the holes Print with full support and file the burgerplates thoroughly flat afterwards. PLA prints need to be lubed to work properly. if you want to replace the sheaves with ball bearings here is some useful information: sheave thickness = rope diameter * sqrt(2) The rope used in my case was: http://www.amazon.de/Seil-Leine-Schnur-16-fach-x20AC/dp/B0085IZ054/ref=sr_1_6?ie=UTF8&qid=1378759292&sr=8-6&keywords=pp+seil