surfaces c and d in fig1 these being relatively displaced in fig3 arm 32 is swung upwardly by solenoid driven arm 34 allowing arm 30 to be pivoted leftwardly under the influence of bolt cam surface a as the bolt is moved leftwardly by door part 22 a spring 37 acts to urge arm 30 clockwise to the position seen in fig1 see spring end 37a bearing on the arm 30 and end 37b bearing on the case iii the second arm 32 and a shuttle 45 associated with the third arm 34 have interfitting elements 32b and 45a and 45b in fig3 and 6 these elements being relatively displaced in fig3 i e arm 34 is displaced upwardly by plunger 36a of solenoid 36 to allow arm 30 to pivot leftwardly in fig3 arm 34 is yieldably held downward in fig1 by the solenoid which is activated or energized to 34 pull in 34 it is clear from the above that the provision of these arms allows a solenoid 36 of lightweight construction to control movement of a heavy duty bolt for a door as for example a building door the three arms located in very compact relation in a small case 11 the solenoid is mounted to.