Abstract: In one embodiment of the present invention, a shirt-locking device comprises a fastening device and a weight slidably mounted on the fastening device. The fastening device includes a central portion having a first end and a second end, the first end of the central portion being in the shape of a pin and the second end of the central portion being in the shape of a cooperating hook for holding the first end in a closed position. The weight is approximately 1 ounce and includes a bore into which the central portion of the fastening device is disposed. In another embodiment of the present invention, a shirt-locking device comprises a fastening device, a generally U-shaped bracket mounted on the fastening device and a weight slidably mounted on the bracket. In use, the fastening device of both shirt-locking device embodiments can be used to affix the bottom portion of a shirt, or other similar material, in a tucked position down and against an undergarment, or other similar garment.