A power rack, also called a squat rack, is a piece of weightlifting equipment designed to be used as a mechanical spotter for free weight barbell exercises, most often squats. The most common design is of four vertical bars in the shape of an upright rectangle with two lower bars, called the bar catches, connecting two of them near the bottom to catch a falling barbell. An alternative design uses only two vertical bars, but maintains the two bar catches. Most often found in gyms.