This is a trailer. 53' away at the other end is a vehicle designed for pulling said trailer. These contraptions go between people’s places of business picking up or delivering goods. Once they have loaded or unloaded, they depart—often in the reverse direction if space is limited.

WHY would you park behind one?

Also, when you see one in the wild, you may notice they are quite big.

HOW do you not notice when it starts moving? And why would you waste time honking instead of getting out of they way? They don’t move very fast and the driver is a long way away.

...

They got off lucky with a bent plate... Still, I don’t understand ending up in that situation in the first place. There are empty parking spaces and a big sign that says not to park in the laneway. And an empty parking lot next door that they went to after being displaced.