掛ける is "to hang something." This is the version where something hangs by itself. At some point someone decided for it to be hung and now it's hanging there. You know this because there is a car (かる) hanging there on the wall. How silly, you certainly didn't hang it, that would be impossible. It's just hanging by itself.
The reading is the same as 掛ける, so as long as you know that you know this too.
When I went to the Louvre, the Mona Lisa was hanging crooked.