The invention provides a fastener (10) for releasably securing a first element, such as an air bag (12) to a second element such as a bracket (14) located in a vehicle. Fastener (10) has a locking pin (16) which is movable between a locked position and a release position. Locking pin (16) has an engageable head (18). Fastener (10) includes clip (22) for engaging head (18). Locking pin (16) is biased to the release position, for example, by spring (26). Fastener (10) includes an actuator such as spring (32), comprising or including shape memory alloy and adapted to elongate upon application of appropriate energy. When spring (32) is elongated, it causes locking pin (16) to move to the release position. The invention also provides a fastener assembly (130) including at least one post (122) having a groove (124). Fastener assembly (130) includes a bar or latch, for example, in the form of wire (126) adapted to engage the groove (124). Attached to bar (126) is connecting means, such as shape memory spring (128). Upon application of suitable energy, spring (128) is adapted to change shape and draw bar (126) out of engagement with groove (124).