A grid key and method for keying exterior grid cells in a nuclear fuel assembly. The grid key has a main body portion having first and second ends and is bent at approximately a 45 degree angle near the first end. Two tabs extend outward from the first end at a right angle to the main body portion to define a T-shape. The T-shape end is inserted into the window of the exterior grid strip such that the top of the T-shape is parallel to the longitudinal axis of the grid assembly. The main body portion is then rotated 90 degrees to position the top of the T-shaped end to be perpendicular to the longitudinal axis of the grid assembly and behind the exterior grid strip. The main body portion is then pulled away from the exterior grid strip in a vertical rotating motion, causing the top of the T-shaped end to pull the exterior grid strip away from the center of the cell defined by the grid assembly.