A device for automatically locking the fly assembly of an extension trestle ladder in an extended or lowered adjustment position. The fly assembly is supported to prevent downward movement by a displaceable member which abuts a rung on the fly assembly along a portion of the length of the rung, which...http://www.google.fr/patents/US4240522?utm_source=gb-gplus-shareBrevet US4240522 - Extension trestle ladder
