One way to ensure that you're getting a quality cover for your lawnmower is to read reviews before making your purchase. Make sure to find a cover that has good ratings and reviews from other people who have bought it. Another way to make sure your cover is waterproof is by using the sealant that comes with the cover. This will help make sure that water doesn't enter the machine and damage it. The cover should also fit well and be secure on the lawnmower. A good fit will avoid water getting inside the machine and onto the engine or other equipment.