Measure the top, sides, front and back of the grill with a measuring tape and record all of your measurements. Add the measurements for the top, front and back to get the dimensions for a rectangle that fits over all three faces of the grill. Add 2 inches to each measurement.
Draw the basic pattern for the grill cover on pattern paper. Draw one rectangle using the dimensions you combined from the top, front and back of the grill. This is the main body of the cover. Draw two separate rectangles for the sides of the grill cover. Cut the patterns out of the pattern paper.
Pin the patterns onto sheets of canvas material. Cut around the patterns to make the three pieces for the grill cover. Pin the pieces together at the edges. Carefully place the cover over the grill to check if it fits. Make any necessary adjustments with your scissors and pin the pieces back together until they fit over the grill.
Fit your sewing machine with an 18-gauge needle and the thread color of your choice. Sew the pieces together, starting at the bottom of one side and making your away around to the bottom of the opposite side. Remove the pins from the finished end. Cut the thread and repeat the process for the other end of the grill cover.
Turn the grill cover inside out and slide it over your grill. Apply a waterproofing spray as directed on the can and allow the grill cover to dry. Apply a second coat of the spray and allow the cover to dry again.