Abstract: A fence assembly of a cut-off machine includes a fence base fixed above a worktable of the cut-off machine, a fence plate supported on and movable along the fence base, having a downwardly extending bottom panel and a locking structure for controlling whether the fence plate is locked to the fence base. The locking structure includes a fastener defining a separation with a constant length from the fence base, a first block, a second block and a press member. The first block, the second block and the bottom panel are positioned in the constant separation. The bottom panel is disposed between the second block and the fence base. The contact surface between the first block and the second block slopes toward the direction of the separation. The first block is movable substantially perpendicularly to the direction of the separation. The press member selectively presses the first block.