These are two rounding jigs for rounding corners in woodworking and furniture making. The possible radius is 10 to 80mm. Designed to be used with router table of handheld router. With movable side stops to allow for better clearance.

Hardware:

4 machine inbus (internal hex head) bolts  M4x20 

16 standard M4 nuts

Assembly: 

Just glue the nuts in their sockets with a dab of CA glue.