A L-shaped bracket having aligned vertical and horizontal slots is mounted on a telescopic stand. A frame member is positioned on a horizontal support plate of the bracket. A bearing plate extends vertically from the support plate. The support plate includes spaced apart open ended slots aligned beneath elongated vertically extending slots in the bearing plate. A J-bolt having a cap at one end and a threaded portion at an opposite end extends through the aligned slots to a position where the cap abuts the bearing plate and the threaded end portion extends down through the slot in the support plate. A bell nut is tightened on the threaded end of the bolt to draw the bolt into clamping engagement with the frame where the bolt is adjustable along the length of the vertical slot in the bearing plate to receive frames of a variable range of height.