A relief member is described. The relief member is suitable for engaging a support member adapted to support a subjects body part and includes a relief member body which includes a body thickness and comprises a relief member body plane disposed along a selected body axis and an engagement means integral with the relief member body and adapted to engage with a support member, the engagement means being movable between a first configuration and an engagement configuration, the engagement means in the first configuration being disposed within extremity boundaries of the body thickness or is disposed substantially within the same plane as the relief member body plane, and the engagement means when in the engagement configuration extending outside the extremity boundaries of the body thickness or outside the relief member body plane to releasably engage the relief member to the support member.
