A structure for positioning a body part includes a support base, and a shell frame having an inner surface configured to a shape of the body part. The shell frame is further configured to ride upon the support base, or upon a carriage that further rides upon the support base, to enable a pitch and/or a roll of the shell frame to be adjusted relative to the support base.本發明揭示一種用於定位一身體部分之結構，其包含一支撐基底及具有經構形成該身體部分之一形狀之一內表面之一外殼框架。該外殼框架進一步經構形以騎置於該支撐基底上，或於進一步騎置於該支撐基底上之一托架上以實現相對於該支撐基底調整該外殼框架之一節距及/或一輥。
