Ways not to lock your bike

When I visit my grandparents in Switzerland I use his bike and something like this is more than sufficient.

Grandfather gets annoyed with me when I take the car keys out the ignition, 'cause he doesn't like looking for them in morning! he he

Those locks are actually really good. about a year ago two bikes got taken out of my garden. they broke all the normal locks and lifted them over the wall. then they set about trying to break those wheel locks but they couldn't. they were cosmetically wrecked but neither of them failed. the other locks the broke were fairly decent too.