I have a square shower grate with two holes holding it down to the drain. I was cleaning the drain the other day and lost a screw. I was curious as if it needs to be there. I ran a piece of fishing line down the hole and it came out and went down the drain. Now the stupid question (more for piece of mind), will it leak into the crawlspace or is it fine? I am not sure what type of drain it is, but can take pictures if need be. I am assuming it's good without a screw, but we all know what happens when you assume......