Abstract: An electro-mechanical lock which includes a housing having right and left side cavities in which a latch block may be selectively mounted to cooperatively retain a tongue extending from a door or gate which slides or swings from either the left or right side. The latch block includes a pivotable "J" latch which is engageable within a slot in the tongue extending from a gate or door to be locked as the tongue engages the "J" latch as the gate or door is closed. A latch retainer is operable to secure the latch in an engaged position with the tongue and is retractable by a solenoid or mechanical element controlled by a key operated cylinder to release the "J" latch and allow opening of the gate or door.