This is one pre-notched 72-inch cross brace that is a great tool to add more durability and stability to your large canvas. A cross brace is necessary when one dimension of your frame is 36-inches or longer. This cross brace will protect your work from bowing and is often necessary as a way to stabilize it. The pre-notching means that you can add another cross brace if your frame has square dimensions or if both its length and width are 36-inches or longer. Pre-notching is convenient as other cross braces require an extra cost to have them notched, and it saves you both time and money.