Service by the Lay

I was biking home tonight and passed a place selling stone. It had a sign out the front; "Full Supply and Lay Service".
As a Christian - gosh I hate that phrase, so usually followed by some judgemental statement about something. As an aside I don't think Jesus ever used that sort of condescending approach, he seems a lot more straight up about things - anyway I digress.
The reason I mention the Christian bit is because probably to others this sign made perfect sense but for some reason my brain was on another track. Lay in a church setting usually refers to people who are not clergy(the ones who are vicars and bishops and stuff). The Lay people are everyone else.
So here I am thinking why are they saying "lay service"? Is their service a step down, dealing with the everyday people not the people set aside to be in charge of the stone? Are they planning a service run by the lay and what has this to do with stone?
Then it clicked.
Oh they lay the stone for you.
I didn't even go to any service on Sunday, Lay or otherwise. But I think I need to get some sleep, my brain has gone weird.