An apparatus for holding a display device, the apparatus comprising: a back plate comprising a rear face and a front face opposite the rear face; and a plurality of engaging members (22A-D) disposed around a periphery of the back plate and extending from the back plate in a direction from the rear face to the front face to define an outer boundary of a retention space configured to accept the display device, the plurality of engaging members (22A-D) including a rotatable engaging member configured to rotate between an engagement position configured to secure the display device within the retention space and a disengagement position configured to allow removal of the display device from the retention space; a locking mechanism configured to prevent rotation of the rotatable engaging member between the engagement position and the disengagement position; characterized in that the locking mechanism includes a first locking portion and a second locking portion, the first locking portion including a first aperture, the second locking portion including a second aperture, each of the first and second locking apertures (74, 76) are configured to receive a locking bar of a removable lock, and the first and second locking portions (70, 72) are positioned to prevent rotation of the rotatable engaging member between the engagement position and the disengagement position when the locking bar of the removable lock is inserted through each of the first and second locking apertures (74, 76); and one or more tensioned guide bearings (46A, 46B) secured to the rear face of the back plate adjacent the rotatable engaging member and connected to the rotatable engaging member to allow movement of the rotatable engaging member along an axis of the back plate between a first position corresponding to the engagement position and a second position corresponding to the disengagement position, wherein the first and second locking portions (70, 72) are positioned to prevent rotation of the rotatable engaging member between the engagement position and the disengagement position when the locking bar of the removable lock is inserted through each of the first and second locking apertures (74, 76) by preventing movement of the rotatable engaging member between the first and second positions. a back plate comprising a rear face and a front face opposite the rear face; and a plurality of engaging members (22A-D) disposed around a periphery of the back plate and extending from the back plate in a direction from the rear face to the front face to define an outer boundary of a retention space configured to accept the display device, the plurality of engaging members (22A-D) including a rotatable engaging member configured to rotate between an engagement position configured to secure the display device within the retention space and a disengagement position configured to allow removal of the display device from the retention space; a locking mechanism configured to prevent rotation of the rotatable engaging member between the engagement position and the disengagement position; characterized in that the locking mechanism includes a first locking portion and a second locking portion, the first locking portion including a first aperture, the second locking portion including a second aperture, each of the first and second locking apertures (74, 76) are configured to receive a locking bar of a removable lock, and the first and second locking portions (70, 72) are positioned to prevent rotation of the rotatable engaging member between the engagement position and the disengagement position when the locking bar of the removable lock is inserted through each of the first and second locking apertures (74, 76); and one or more tensioned guide bearings (46A, 46B) secured to the rear face of the back plate adjacent the rotatable engaging member and connected to the rotatable engaging member to allow movement of the rotatable engaging member along an axis of the back plate between a first position corresponding to the engagement position and a second position corresponding to the disengagement position, wherein the first and second locking portions (70, 72) are positioned to prevent rotation of the rotatable engaging member between the engagement position and the disengagement position when the locking bar of the removable lock is inserted through each of the first and second locking apertures (74, 76) by preventing movement of the rotatable engaging member between the first and second positions.