Secure the valve box cover onto the valve box with the corrosion-resistant Stainless Steel Bolt. The bolt diameter is 3/8 in. and length is 2-1/2 in. Works with the patented Universal Locking Mechanism (ULM) feature built into select valve boxes such as the 14 in. X 19 in. Standard Series and Pro-Spec® Series Valve Boxes to fasten the cover without the use of a nut