surfaces and to move upwardly this causes the lower ends of all of the locking members 30 32 34 and 36 to pivot outwardly to the position of the operating member 36 shown in the left hand side of split fig2 when the lower outer edge of the locking members 30 32 34 and 36 engage the wall 12 of the manhole shaft the cover 16 firmly is held in place against removal if desired the lower outer portions of the wedge shaped members 30 32 34 and 36 also may include some frictional material either built into this portion of these members or placed on the outer surface to increase the holding force of the device it should be noted however that the conical operator 40 is threaded upwardly to a position which creates a substantial amount of force on the lower edges of the hinged locking wedges 30 32 34 and 36 so that such additional frictional surface on these members may not be necessary once the device is locked in place as shown in the left hand side of the cross section of fig2 and for the member 36 shown in fig4 the operating rod 44 45 is removed the device remains locked in place so that accidental or unauthorized removal of the cover 16 is not possible because the.