a compact push - pull right - angle lock especially suited for use on patio doors and on windows has a cylindrical bolt with rack teeth on its central section , a barrel lock assembly , and a rotatable disk all contained in a horizontally split case . the bolt can be extended in either direction by the right angled linear motion of the barrel lock assembly . linear motion of the barrel lock assembly is transferred to linear motion of the bolt through a disk that is free to rotate some fifty degrees about a shaft . the barrel lock assembly is loosely linked to a crank pin set perpendicularly to the plane of the disk and the bolt rack is meshed with an arcuate section of a pinion gear on the disk located some ninety degrees from the crank pin . the bolt can be locked in either extended position by means of a cam lug which cna be moved from the barrel lock assembly housing into locking recesses in the case by rotational movement of the keyed barrel lock . means are also provided for replacement of the barrel lock when necessary .