I have found that when the screws pull out, either the wood underneath has been wet or the screws were too short to begin with. I usually drill extra holes in the outer trim strip and use 1.5 to 2 inch screws to secure the trim strip. 99% of the time this works. Trying to use toothpicks will NOT work in the long run. With longer screws you get into the wood farther to get enough of the threads to hold. Once you have secured it with longer screws, remove the screws and inject silicone type sealant into the holes and reinstall the longer screws. THEN make sure you seal the outer trim strip especially on top the screw heads. Doug