Can anyone tell me what the quarter inch groove under my exterior window sill is? It is on every window sill and runs the length of the sill about 1 inch in from the edge. My wooden clapboard house was built in 1946. I am having the siding replaced by my contractor and he is going to put quarter round under the window sills but that will cover up the groove. Is it some drip thing? Is it ok to cover it up? Hope someone knows. I need to know soon so I don't do something that will hurt the sill. Thanks.