A vandal-resistant frame has a rear member securable to a relatively vertical supporting surface and a front member hinged to the rear member for movement between open and closed positions. The front member has an aperture through which advertising, photographic or like material within the frame can be seen from an external position. The front member is secured to the rear member in a closed position by at least one projection on one member engaged in a recess in the other member adjacent to the aperture in the front member, whereby the projection or projections can be detached from the recess or recesses to open the frame by an appropriately shaped key member inserted between the front and rear members from a position within the aperture.