Sometimes inner stops are nailed on, sometimes they are screwed on. A stop that is screwed on has the advantage of being adjustable. When a sash swells during the humid summer months, an adjustable stop can be pulled away from the sash to keep the sash from sticking. Likewise, when cold drafts sneak around the stops during the winter months, the stops can be adjusted toward the sash to seal up this gap. In order to adjust an inner stop the screw hole must be larger than the screw shank to allow for movement. (The decorative washer will cover the large hole and allow for the screw head to be properly seated.) Also, in order for a stop to move, it is imperative that it not be stuck with paint to the casing or jamb. For this reason, it is often easier to adjust the stops on windows that have been stained than those that have been painted.
Many times there are 5 screws in a stop. And often the second hole from the bottom lands in the kerf cut for the weight chamber access door; creating a large screw hole that can’t be tightened. While not a great solution, this problem can easily be solved by shimming around the hole with thin pieces of wood (like match sticks) or by adding a plastic anchor.
When nailing stops, be judicious with the number of nails you use. Often there are many nails when normally only three are needed – one, just above the meeting rail, and one each near the top and bottom of the stop.
To fill nail holes, use a thin spatula or utility knife tip to dab a tiny bit of a crayon wood filler into the hole.
To remove paint from screw slots use picks, like the ones pictured above. A set of 4 picks is available from Harbor Freight for 2 or 3 dollars. Repeated scoring of the slot will gradually remove enough paint so you can fit a screwdriver in the slot. Err on the side of removing too much paint or you can risk stripping the screw. If the screw is buried in a hole filled with paint, first use a cheap 1/4″ chisel to dig out the paint.