An assembly (100, 400) installable in a hole of a workpiece (110, 584), the assembly comprising: a non-metallic cage configured and dimensioned to receive and retain nuts having different configurations one at a time, the cage including a first flexible retention element including a first opening; a second flexible retention element including a second opening, the first flexible retention element and the second flexible retention element being spaced apart to receive a nut therebetween; and an abutment portion (144, 540) for lying against the workpiece (110, 584), the abutment portion defining a throughhole; and a retainer with a mounting section and a tubular section including a mounting plate receivable by the cage; and an expandable member connected to the mounting plate and dimensioned to pass through the throughhole (480, 530) of the abutment portion and fit into the hole of the workpiece when the mounting plate is received by the cage, the mounting plate holding the abutment portion of the cage against the workpiece when the mounting section is received by the cage, the expandable member being expandable to form an interference fit with the workpiece while the abutment portion is between the mounting plate and the workpiece. a non-metallic cage configured and dimensioned to receive and retain nuts having different configurations one at a time, the cage including a first flexible retention element including a first opening; a second flexible retention element including a second opening, the first flexible retention element and the second flexible retention element being spaced apart to receive a nut therebetween; and an abutment portion (144, 540) for lying against the workpiece (110, 584), the abutment portion defining a throughhole; and a first flexible retention element including a first opening; a second flexible retention element including a second opening, the first flexible retention element and the second flexible retention element being spaced apart to receive a nut therebetween; and an abutment portion (144, 540) for lying against the workpiece (110, 584), the abutment portion defining a throughhole; and a retainer with a mounting section and a tubular section including a mounting plate receivable by the cage; and an expandable member connected to the mounting plate and dimensioned to pass through the throughhole (480, 530) of the abutment portion and fit into the hole of the workpiece when the mounting plate is received by the cage, the mounting plate holding the abutment portion of the cage against the workpiece when the mounting section is received by the cage, the expandable member being expandable to form an interference fit with the workpiece while the abutment portion is between the mounting plate and the workpiece. a mounting plate receivable by the cage; and an expandable member connected to the mounting plate and dimensioned to pass through the throughhole (480, 530) of the abutment portion and fit into the hole of the workpiece when the mounting plate is received by the cage, the mounting plate holding the abutment portion of the cage against the workpiece when the mounting section is received by the cage, the expandable member being expandable to form an interference fit with the workpiece while the abutment portion is between the mounting plate and the workpiece.