various locations and orientations to be described later v shaped grooves are preferred because of the relative ease in machining them they also permit the support post 22 to self align with the round stock material of frame member 20 and thus compensate for any manufacturing tolerances in addition making adjustments like placing the support post 22 at an angle with respect to a vertical axis in order to compensate for a special painting situation may be accomplished easily through the relative interaction between round stock material and v shaped groove 46 the support post 22 is removably attached to the frame member 20 with a plate 48 secured with a pair of releasable fasteners 50 only one of which is shown plate 48 together with base 44 and fasteners 50 form a clamp 51 preferably the plate 48 extends diagonally across base 44 to increase the amount of surface contact between clamp 51 and frame member 20 for increased holding power it will be apparent that the support post 22 may be positioned virtually anywhere on a straight portion of the frame member 20 the support post 22 may also be positioned directly over the point of attachment of longitudinal section 24 and the transverse section 28 in which case it is preferable to include an appropriately sized hole 45 fig1 in the underside surface of base 44 at the intersection of grooves 46 to provide clearance for a weld bead which may project from the frame at the junction of sections 24 and 28 there is a slot 56 in support post 22 to which.