Center Finder Jig
Simple center finder.
MDF
Cut two pieces of MDF.
Glue
Glue and clamp them at a right angle.
Screw
Reinforce the joint with screws and check for square.
Angle
Cut a right angled triangle piece of MDF.
Glue
Glue and clamp in place.
Pivot Screw
Before the glue dries insert one screw to reinforce and to pivot. Check the 45 degree angle and adjust appropriately, then insert a second screw.
Seal
Seal the edges of the MDF with glue and give the piece a coat of shellac to prevent moisture from warping the shape.