An insert (1) for a weep hole opening in a masonry wall is disclosed. The insert (1) includes a hollow body (2) defining an air flow conduit (3) and including a first open end (4) and a second open end (5). A stainless steel mesh screen (6) extends across the conduit (3) near the first open end (4) and is adapted to prevent fire brands and sparks from passing through the body (2). A locating member, in the form of a grate (7), is hingedly connected to the body (2) adjacent the first open end (4). The screen (6) is located in a recess (8) in the rear of the grate (7) and friction between the screen (6) and the grate (7) retains the screen (6) in the recess (8). The grate (7) is formed from a material that substantially retains its spatial integrity when exposed to the heat flux profile generated by a typical forest fire, such that the grate (7) continues thereafter to locate the screen (6). The grate (7) also has a plurality of ventilation apertures (9) to allow air to pass through the air flow conduit (3). A mortar guard (10) releasably snap-lockingly engages the grate (7) to cover the ventilation apertures (9) to prevent mortar clogging the apertures (9) during rendering.