Porsche Boxster Owner's Manual page 296

Tying down vehicle on at bed
1. Carefully feed towing straps through the
opening in the rear wheels. Make sure metal
parts of straps do not damage rim. Make sure
the strap is flat over the rim bead. Make sure
brake backing plate is not damaged.
2. Secure straps to rear of flat bed.
3. Reel in hoist cable only far enough to tension
tie-down straps.
4. Carefully feed towing straps through the
opening in the front wheels. Make sure metal
parts of straps do not damage rim. Make sure
the strap is flat over the rim bead. Make sure
brake backing plate is not damaged.
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Practical Tips, Emergency Service
5. Secure straps to front of flat bed.
6. Release tension on hoist cable, but do not
disconnect. Use hoist cable as a safety cable.