a1694 A. Balfour (1700) ii. 52 Some few Rooms clacht up against the face of a Rock, like a Bird cage upon the side of a Wall.
1825 J. Jamieson Suppl. (at cited word) Clash up, To cause one object to adhere to another, by means of mortar, or otherwise. It generally implies the idea of projection on the part of the object adhering.