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I know that it's possible to make in Source two boxes - one still and the other moving, attached to it with a rope . I did that in HL2M. One box was about 7 meters above the floor and the other was attached to it on a 2 meter rope, swinging in the air.
However when I played the map in CS:S (of course after changing some textures and player spawn names) the box that was supposed to be swinging on a rope was not there and the rope was noclipping through the floor, as if it was too long and let the attached box noclip with it.