base plate 21 has an upper plate 50 on which the article will rest a peripheral skirt 51 extends around it and extends downwardly to cover the edges of the mat thereby to frustrate the insertion of tools or wires that might be able to pry the mat from the surface optional ribs 52 project downwardly from the plate they are intended to bear against the top of the mat and press the mat against the surface more reliably they are not adhesively bonded to the mat the only adhesive bond is between the bottom of the mat and the surface on which the mat is laid the upper plate of the base plate is provided with four bores 55 56 57 58 each of which is aligned with a respective post 45 bolts 60 are passed through each of these bores and are threaded into respective posts 45 these bolts are the means to hold the base plate to the adhesive mat and consequently to the surface when the bolts at bores 55 and 58 are tightened they function only to hold the base plate to the mat the bolts at bores 56 and 57 serve the additional function of assisting in the adjustment and holding of the rear brackets each rear bracket fig7 10 comprises a base bracket 70 and an upper bracket 71 the base bracket includes a flat slide portion 72 which bears against the base plate a slot 73 extends along the slide portion to pass a bolt 60 which is threaded into.