Locking up yak on roadtrip

[FishNinjaY]

Originally Posted by CheapPelican

In addition to running chain through a scupper, I lay pair of these window alarms in the hull and leave the hatch open. If some one does manage to get past the chain and unload the kayak, the alarm will slide around and go off. Just don't forget to remove them before you drive away.

clever!

I have a few of those. I don't get the "leave the hatch open" part? You just lay these inside, with the magnet near the alarm? so if the kayak is moved, the pieces will move apart and alarm, right? You don't fix it to the kayak and your rack or car or chain? Am I overthinking this? Thanks for the tip.