This is my take on a pair of pipe restraints.
To assemble these you need:
4x M4x50 Caphead bolts
4x M4 Nuts
There is a hole in the side of the pipe restraints to enable them to be attached to things or to attach accessories to them. this is sized for an M6 bolt
They are best printing on standing up like in the picture. The nut hole being on the bed and some supports used in the hinge area and nut hole.
One side of the hinge is curved, this is to allow the cuffs to pivot open on this side. So you only have to undo the bolt on the opposite side to open them
I have also attached the F3D file so you can open them in fusion if you wish to adjust them. Their are some parameters for the wrist width and height so you can easily adjust to your pipes