An adjustable mounting bracket for secure adhesive mounting onto an exposed edge of a substrate, wherein the mounting bracket is adapted for subsequently supporting a selected structure such as tubing, wire bundles, etc., relative to the substrate. The mounting bracket includes slidably interfitting, generally L-shaped bracket members which cooperatively define a slidably overlying pair of mounting plates and an associated pair of slidably separable clamp jaw plates having inboard faces carrying a selected bonding agent and adapted to seat firmly against opposed substrate edge surfaces. A resilient fixture pin is carried by the mounting plates and can be actuated to apply a positive force urging the clamp jaw plates against the opposed surfaces of the substrate edge of the duration of a bonding agent cure time, after which the fixture pin can be forcibly removed from the mounting bracket.