Gather all of your materials. For this project, you'll need one durable plastic sandwich bag with a slide zipper and a paper hole puncher. Choose a plastic zipper bag that will accommodate your pens, pencils, erasers, or other items you wish to store
Mark the bottom of the bag.The bottom of the bag is the side opposite of the zipper end. To get the holes in the right place, lay the bag in a binder, next to the clasps. Then mark two spots for holes on the bag so that when you punch the holes, the holes will line up with the clasps in the binder
* Mark the spots close to the edge of the bag. Around half an inch from the edge should work fine.
Hole punch the bottom of the bag. Use the hole puncher to make two holes in the place you marked them
Reinforce the holes. This step is optional, but if you want your plastic bag pencil case to last longer, you may want to reinforce the punched holes. You can do so with reinforcement labels, which can be found at any office supply stores. These are small circular stickers that can simply be placed around a punched hole in order to prevent the binder from wearing and tearing it. Place the reinforcement labels on all sides of all the holes in the plastic bag.
Click your pencil case into your binder. Fill the bag with your pens and pencils and you're done!