Four of these feet will support a Mendel deposition bed. The semi-circular recess rests on the Y rails, so no bearings are required. The bed can be levelled by tightening the 2 Nylok nuts on each foot, thus compressing the spring structure.

The heads of the two M4x40 machine screws are recessed into the attachment bracket, and three small holes are provided. These nicely take No.4 3/8" to 1/2" countersunk or pan-head woodscrews - the SCAD file has an option for it. The M4 screws are held captive by two nuts which are recessed, so no washers needed there.

This allows just one layer of bed to provide an adjustable flat upper surface for deposition.

Works best in PLA as this gives low friction. Washers are needed under the Nylok nuts. Two ordinary nuts may be locked off on one another in place of each Nylok.

The same feet will happily run on 1/4" steel piano or music wire with no modification other than a little lubrication.

Full assembly details for the Y-Bed are here: http://reprap.org/wiki/Y_Bed_Simplified