Just kidding.
I block them by putting a transparent cup over them, slide an open book cover beneath where they stand, so that they must enter on top of it, close the book, and off we go - I, the book, the cup that I press with all my force, and the spider trapped inside - to the nearest opening in the building, wishing them the very best on their new way of life, outside, and for me to live and thrive.
In my apartment, and I swear this is not a joke, most of the time I use "NoSQL - A Brief Guide to the Emerging World of Polyglot Persistence - Distilled", as my main transport mechanism.
Anyway, to the point. Similarly interesting behaviors of spiders include using web vibrations for communication and sensing, apparently even including tuning. You can easily google (is this still a cool way of saying "search"?) related articles, just ignore the web apps Vibrations API article on the MDN.