An apparatus for adjusting an active length of a plurality of interwoven support elements of a weight bearing surface to conform to contours of a user's anatomy, the apparatus comprising: a plurality of interwoven support elements (113, 114) forming the weight bearing surface; a frame which the weight bearing surface overlies and to which the plurality of interwoven support elements (113, 114) are connected, and an adjustment mechanism (166, 180) connected to one of the plurality of interwoven support elements (113, 114); wherein the adjustment mechanism (166, 180) allows the active length of the connected interwoven support element to change as a user bears upon the weight bearing surface, thereby conforming the weight bearing surface to the contours of the user's anatomy, characterised in that the adjustment mechanism (166, 180) is a one-way ratchet mechanism for adjusting the length of the support element that locks for maintaining an adjusted position of the plurality of interwoven support elements (113,114) and that is attached or releasably attached to one side of the frame to tension the interwoven support element extending from the adjustment mechanism (166, 180) to the other side of the frame, the one-way ratchet mechanism comprising a ratchet strap connected to the interwoven support element (113, 114), and in that the adjustment mechanism comprises a tensioner to control the amount of force required to lengthen the interwoven support element (113, 114). a plurality of interwoven support elements (113, 114) forming the weight bearing surface; a frame which the weight bearing surface overlies and to which the plurality of interwoven support elements (113, 114) are connected, and an adjustment mechanism (166, 180) connected to one of the plurality of interwoven support elements (113, 114); wherein the adjustment mechanism (166, 180) allows the active length of the connected interwoven support element to change as a user bears upon the weight bearing surface, thereby conforming the weight bearing surface to the contours of the user's anatomy, characterised in that the adjustment mechanism (166, 180) is a one-way ratchet mechanism for adjusting the length of the support element that locks for maintaining an adjusted position of the plurality of interwoven support elements (113,114) and that is attached or releasably attached to one side of the frame to tension the interwoven support element extending from the adjustment mechanism (166, 180) to the other side of the frame, the one-way ratchet mechanism comprising a ratchet strap connected to the interwoven support element (113, 114), and in that the adjustment mechanism comprises a tensioner to control the amount of force required to lengthen the interwoven support element (113, 114). an adjustment mechanism (166, 180) connected to one of the plurality of interwoven support elements (113, 114); wherein the adjustment mechanism (166, 180) allows the active length of the connected interwoven support element to change as a user bears upon the weight bearing surface, thereby conforming the weight bearing surface to the contours of the user's anatomy, characterised in that the adjustment mechanism (166, 180) is a one-way ratchet mechanism for adjusting the length of the support element that locks for maintaining an adjusted position of the plurality of interwoven support elements (113,114) and that is attached or releasably attached to one side of the frame to tension the interwoven support element extending from the adjustment mechanism (166, 180) to the other side of the frame, the one-way ratchet mechanism comprising a ratchet strap connected to the interwoven support element (113, 114), and in that the adjustment mechanism comprises a tensioner to control the amount of force required to lengthen the interwoven support element (113, 114).