showed schematically as spring 52 to receive hook portion 30 when hook portion 30 is moved into position 29 b shown in fig2 then to hold the hook portion 30 against upward motion the trap 40 includes an aperture 63 at its left edge when the trap 40 is retracted leftward capturing the hook portion 30 the aperture 63 aligns with a blocking element 54 which may descend into the aperture 63 from an actuator mechanism 55 positioned above the trap 40 in this configuration rightward movement of the trap 40 is stopped by interference between a left surface of the blocking element 54 abutting a blockade surface 53 forming a left wall of the aperture 63 thus the trap 40 acts as a trap to hold the bolt 26 in position when the blocking element 54 acts as a blocking element to the trap 40 referring now to fig5 6 a and 9 the blocking element 54 may be moved downward under the influence of a flexible leaf spring 56 the flexible leaf spring 56 holding one of a pair of contacts of a lock switch 57 indicating proper locking of the latch 25 when the blocking element 54 is lowered and the contacts connect closing the lock switch 57 at this time the blocking element 54 may only be disengaged by action of a bistable solenoid mechanism 60 shown schematically in fig5 and described below providing a wedge element 58 that may lift the leaf spring 56 to raise the blocking element 54 by contacting a sloped portion 59 of the leaf spring 56 referring again to fig5 the blockade surface 53 may be formed by a thin member that can break away.