PURPOSE: To pinch the copying paper for sure by fitting a compression spring to a sleeve to pinch and press both sides of latch section pieces.

CONSTITUTION: A pair of sleeves are inserted from both sides of a main body 7 of a lock device so as to slide along a suitable gide bar 1, and in addition, latch section pieces 2, 2' are pivoted to the main body 7 of the lock device. Compression springs 3, 4 with different rebounding forces are fitted to sleeves 5, 6 respectively so that the latch section pieces 2, 2' are pinched and pressed by the sleeves 5, 6 in the main body 7 of the lock device. Furthermore, the latch section pieces 2, 2' pivoted to the main body 7 of the lock device are arranged so that they get into contact with the guide bar 1 when they are rotated in the direction which is pressed by one of the sleeves 5, 6 having a stronger rebounding force. According to this constitution, the located side guide can be fixed for sure, and the copying paper can firmly be pinced.