Collect a few plastic drink bottles. Remove the lids and soak the bottles in hot, soapy water for several minutes to clean the bottle and remove the paper label. Rinse the bottles and lids and dry the bottles thoroughly. Decorate the bottles with paint or markers before cutting the plastic. Find the stick your windmill will be attached to. The stick will vary depending on the type of windmill you are making.
Measure and mark each bottle to place three vanes equal distances apart. The vanes will have one side that is a straight vertical line, starting one inch from the bottom of the bottle and stopping one inch below the narrowing of the bottle neck. At the top of the line draw a one-inch horizontal line to the left. At the bottom draw a two-inch horizontal line to the left. Connect the two horizontal lines by drawing a vertical line from the one-inch line to the two-inch line. Your drawing will look like a flap. Draw two similar vanes on the bottle. Use a razor knife to cut the vane on three sides, leaving the straight side untouched and fold the vanes inward so they are inside the bottle. Use a power drill to drill a hole in the bottom of the bottle large enough to pass a stick through. Lead the stick through the hole in the bottom of the bottle, drive the stick into the ground and wait for a breeze. If you want to make another type windmill, follow these instructions but bend the vanes outward.
Use a sharp knife to cut the bottom off a clean water or plastic soda bottle one to two inches deep. Use care and cut five equally spaced square holes, one1 inch by ½ inch with a sharp knife in the bottle bottom. Your bottle bottom will resemble a pinwheel. To avoid splitting the plastic, use a power drill to drill a hole larger than your nail, in the middle of your plastic piece where the nail will eventually go. Use scissors to cut a piece of plastic three inches long and as wide as your wooden stake for a back plate. Attach the back plate to the top of the stake with small nails or a stapler. Nail your plastic pinwheel piece to the center of the back plate, making sure your pinwheel can turn freely. Pound the stake into the ground and watch your windmill spin.
Cutting a plastic bottle with a sharp tool can be too dangerous for children. Adults should cut the plastic bottle and use any power tools for this project. Cut plastic can have sharp edges, use caution.