To replace a windowsill, first remove the old sill by prying it away from the window frame. Clean the area and ensure it’s level. Cut a new sill to size, install it in place with adhesive and screws, and finish by sealing around the edges.

Replacing a windowsill involves removing the old sill, preparing the area, and installing a new one. Proper leveling and sealing are crucial for durability and preventing water damage.