They've given you the desk by the door. Has it crossed your mind they might be trying to tell you something?
I used to live in an upstairs flat. For some reason the fat boiler downstairs used to slam the front door shut and the whole hoose used to shake. One day I wrote her a nice letter asking her to consider how uncomfortable she was making it for us, the family upstairs. This irked the fat **** and she started slamming it more often. So, in response I started to trip my house alarm every time she slammed the front door. It would sound (loudly of course) for 30 mintues. I even wrote her a nice letter telling her that her door slamming triggered my alarm. The tripping of my alarm often stopped her brat child from having a nap of an afternoon which fat boiler **** neighbour clearly looked forward to. When fat boiler realised what was happening, she stopped slamming the front doot and had it planed down. I continued tripping the alarm though. I won.
That's a great example of how to handle ****s like that. You make them want what you want them to do. Good work, sir.
Have a **** and catch the muck in your hand, go to the door and wipe the goo all over the handle. It won't stop them going in and out but at least you can A) enjoy a bit of solo afternoon delight and B) have a chuckle each time someone gets sticky fingers