To tie down a golf cart in a truck mattress, comply with the steps: 1. Position the golf cart inside the truck bed and set the parking brake. 2. Use at least two high-quality nylon straps with ratchets. 3. Attach one end of each strap to stable points on the golf cart, such as the frame or axle. 4. The other gives up to anchor points within the truck bed. 5. Tighten the straps using the ratchets until the golf cart is firmly secured and has minimal movement. 6. Double-test that the straps aren't over-tightened to keep away from unfavorable golf carts.