Model originally uploaded to Thingiverse at https://www.thingiverse.com/thing:1656880.
Update, 27th January 2019 Added a version with two screw holes for mounting to underside of shelf This is the preferred version as both sides are now more robust.
Update 30th October 2017
I've added a revised version with the upper screw hole part removed on one side.
This is to allow a little more flexibility in the plastic around the screw clamp area.
This is a bracket I designed to allow a full size shelf to be fitted at any height underneath an Ikea table fitted with Adils 40mm legs.
The bracket clamps around the legs, just slide onto the leg and lock in place at the desired height using a 25mm (approx) 4mm bolt, tighten enough to stop the bracket sliding, if it won't twist on the leg using reasonable force, then it's tight enough.
There are two screw holes in the top of the bracket to attach to the shelf. And one hole on the updated version,