<human>:  Please furnish a step-by-step guide on how to build a bookshelf.
<bot>: 
1. Gather the necessary materials: plywood, screws, saw, drill, and necessary tools.
2. Measure the space you will be placing your bookshelf and calculate the size of the shelf and sides.
3. Cut the plywood to size, using the saw or jigsaw.
4. Make sure the edges are smooth and sand if necessary.
5. Mark where you need to attach the shelf supports.
6. Use a drill to make holes for screws to attach the shelf supports to the sides.
7. Sandwich the sides between the shelf supports and attach the screws.
8. Turn the bookshelf over to make sure everything is secure.
9. Place the completed bookshelf in the desired space.
10. Secure the bookshelf by screwing it to the wall if necessary.