In a safe deposit locker installation comprising an array of individual safe deposit lockers (1) disposed in adjacent vertical rows (R 1 - R 10 ) vertical penetration-resistant bars (2) are borne externally of the lockers for horizontal sliding movement (or pivotal movement - Figure 3 not shown) immediately in front of the lockers (1). Each bar (2) can be locked in place in front of a respective row of lockers so as to block the doors (21) of the lockers in that row from opening, and the bars (2) can be displaced one at a time to unblock the respective row (eg R 5 ) without disturbing the other locked bars.