Segals. They install carseats even if they weren't purchased there, and no appointment is necessary. Fire departments and hospitals often have clinics on the weekends, but the line was soooo long when we tried that route.
My husband took our cars to our local police station in Clackamas and an officer walked him through the proper way to install the car seat and how to do routine checks on making sure it wasn't loosening on its own as you begin to use it over and over.
Segal's, as others have noted- or a certified car seat safety inspector at your local police/fire station. I was able to get an appt. within a couple of days with one near me.
You can also go to the Beaverton Police Station. ?They have Carseat Installation clinics a few times a month where ceritified officers install your carseat. ?The officer who installed ours had it so snug, we've never been able to get the seat in as tight as he did.
Re: Carseat install?