Round guides b of link 3 fit into holes in prongs a of link 1. Round guide e of link 4 fits into body c of link 3. Pin h of link 2 fits into a hole in body f of link 4. With respect to each other, links 1 and 2 accomplish three turning motions about two perpendicular axes x-x and y-y, and about axis x' -x' (parallel to axis x-x), and two translational motions along axes x-x and y-y.
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