A reformer exercise apparatus comprising: a rectangular frame having a head end member , a foot end member and a pair of spaced parallel side members ; and a corner member joining at least each side member to one of the head and foot end members , characterized by the corner member comprising: an elongated hollow metal extrusion having, in cross section, a central corner portion and two leg portions each extending from the central corner portion at a right angle to the other leg portion , each leg portion having an inner side wall spaced from an outer side wall parallel to the inner side wall and merging with the central corner portion , and an outer end wall joining the inner and outer side walls ; the inner and outer side walls each having an inner surface facing the inner surface of the other side wall , and an opening through the outer end wall defining a space between the inner and outer side walls adjacent one end of the extrusion for receiving one end of one of the frame side members and end members ; wherein at least one of the inner surfaces of the side walls in the space has discrete surface features adapted to grip and retain the one end of one of the side members and end members in the space when received through the opening . a rectangular frame having a head end member , a foot end member and a pair of spaced parallel side members ; and a corner member joining at least each side member to one of the head and foot end members , characterized by the corner member comprising: an elongated hollow metal extrusion having, in cross section, a central corner portion and two leg portions each extending from the central corner portion at a right angle to the other leg portion , each leg portion having an inner side wall spaced from an outer side wall parallel to the inner side wall and merging with the central corner portion , and an outer end wall joining the inner and outer side walls ; the inner and outer side walls each having an inner surface facing the inner surface of the other side wall , and an opening through the outer end wall defining a space between the inner and outer side walls adjacent one end of the extrusion for receiving one end of one of the frame side members and end members ; wherein at least one of the inner surfaces of the side walls in the space has discrete surface features adapted to grip and retain the one end of one of the side members and end members in the space when received through the opening . an elongated hollow metal extrusion having, in cross section, a central corner portion and two leg portions each extending from the central corner portion at a right angle to the other leg portion , each leg portion having an inner side wall spaced from an outer side wall parallel to the inner side wall and merging with the central corner portion , and an outer end wall joining the inner and outer side walls ; the inner and outer side walls each having an inner surface facing the inner surface of the other side wall , and an opening through the outer end wall defining a space between the inner and outer side walls adjacent one end of the extrusion for receiving one end of one of the frame side members and end members ; wherein at least one of the inner surfaces of the side walls in the space has discrete surface features adapted to grip and retain the one end of one of the side members and end members in the space when received through the opening . <EOS>