Abstract: A face seal acts across a gap between first and second machine, particularly a gas turbine, components operating at elevated temperatures. One end of a sealing element is housed in a recess in the first component and its other end seals against a plane surface of the second component under the action of a spring. To allow assembly of the components and the seal within, say, a gas turbine engine without damaging the seal or other components, the sealing element is temporarily retained entirely within the recess by a latch, the latch being temperature-sensitive and operative only once to release the sealing element to perform its sealing function at a predetermined elevated temperature. The latch may be a fusible pin.