Thomas performs an inspection of the underside of a sink to show how roaches get in. They move to the pipes because of surface moisture on them and then follow them along the inside of your walls to an opening crack. Here they are granted access to your bathroom, and your whole house.
So I am inspecting under the sink right now, because the piping is where the roaches will travel along most frequently. Its got the moisture, its got everything on the pipe, and a lot of these roaches will come up the pipes; just crawl right up the pipes and crawl into your bathroom spaces from the pipes. Most pipes are going to have a little bit of an area around, where the pipe comes out of the wall. Enough space for the roaches to climb into your bathroom.