Have you ever tried to tie your trunk or hatchback down on a newer car and find there is nothing to tie to?
Step 1: Tie Down
Some time ago it hit me to stuff something into the locking mechanism. At the time all I had to use was a old 1/4 in. Zinc-Plated Quick Link but a cheap carabiner works fine. Between the carabiner and the bottom trunk latch you have two good tie down points.
Step 2: Release
When it's time to unload just hit the trunk release. Untie after unloading.