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Lay the toilet seat on top of a piece of 1⁄2 inch (1.3 cm) plywood and use a pencil or marker to trace around the interior hole and the outside of the seat. Be sure to mark the holes in the back where the seat will be screwed into the plywood, as well. If possible, add a second, slightly larger circle around the tracing of the interior hole and plan to cut along this second line so that your piece of plywood is smaller than the actual toilet seat. This will make it less likely for waste to accidentally get onto the plywood. and drill out the attachment holes. Cut along the exterior tracing first, then cut out the tracing of the interior hole. Use a drill bit that is equal in size to the bolts you’re using to attach the seat to the plywood.  Your toilet seat most likely came with bolts and nuts that you’re meant to use to install it. If for some reason you’re missing these materials, bolts that are 5⁄8 inch (1.6 cm) in diameter will probably work for your toilet. If you plan on using a chair for your camping toilet, be sure to drill a hole in the chair that is the same size as the interior hole of your plywood piece. These will act as stoppers to prevent the toilet seat from sliding off of the bucket or out of the chair when you go to use it. Use nails or screws to attach the wood pieces to the bottom of the plywood on all 4 sides.  Drive a nail or a screw down through the plywood piece and into each piece of wood in order to attach them. These wood pieces can be any size or shape, as long as they fit inside of the bucket. For best results, use pieces that are at least 2 inches (5.1 cm) long and that aren’t wider than the toilet seat itself. Screw the bolts through the hinge on the back of the toilet seat and through the drill holes on the back of the plywood piece. Attach the nuts to the ends of the bolts on the underside of the plywood to secure the plywood to the toilet seat. The hinge is the plastic piece on the back of the toilet seat that connects it to the lid. Push the seat through the hole in the chair if you’re using one, or simply place it over the top of your bucket. Make sure all 4 bottom pieces of wood fit snugly and securely in the bucket or in the hole in the chair. Be sure to place a bucket underneath your chair before you use your new camping toilet.

Summary:
Trace the outer and inner circumferences of the toilet seat on plywood. Cut out the tracing with a jigsaw Attach 4 small blocks of wood to the bottom of the plywood piece. Secure the toilet seat to the plywood with bolts and nuts. Place the toilet seat over your bucket or chair to finish your toilet.