121 passes through the clamp 120 through a hole cut in the planar material 40 and through a hole in the l shaped base 122 where it is held in place by a nut 123 not visible in fig6 the l shaped base 122 and clamp 120 are made from any sturdy material preferably aluminum steel stainless steel ultra high molecular weight plastic uhmw or a structural plastic such as glass filled polypropylene referring to fig7 a second perspective view of an adjustable support 110 of a second embodiment of the present invention is shown an l shaped base 122 and clamp 120 are configured to sandwich a planar sheet of material 40 shown in fig4 in an aperture 160 the base serrations 114 are angled toward the base 122 bottom while the clamp serrations 112 are angled away from the base 122 bottom thereby engaging with each other to hold the clamp 120 in position with respect to the base 122 while inserting and tightening screws as shown in fig3 creating an aperture 160 of desired size the locking pin 131 and locking pin handle 130 are shown in position of being engaged with the opposing support surfaces 47 48 to release the clip from the opposing support surfaces 47 48 the locking pin handle 130 is rotated 90 degrees to a point where it clears the locking pin retainer 135 at which point it can be easily pulled to disengage from the hole in.