Measure the size of the pump so you know how large to make your screen. Many pumps are in housings dug into the ground, so use a tape measure to gauge the size of the opening.
Drill together a frame that is slightly larger than the pump housing. Use plywood planks at least 1 inch thick. The thickness provides both weight and durability so the screen stays in place and the frame doesn't break. Either cut the planks yourself using a circular saw or get pre-cut planks from a hardware store. Drill two screws into each end of the planks to hold them together to form a square.
Unroll a screen over the framework and staple it in place using a construction stapler. Place a staple every few inches to ensure the screen doesn't pull loose. Staple the screen all the way around the frame for best results.
Cut any excess screening around the frame using scissors. This helps prevent the screen from snagging debris as it blows by and also makes it less likely the screen will pull away from the frame.