Questions about sealing wood

[whatsherface]

I'd get the plexi from a glass shop. it will be cheaper and I've seen a lot of stuff pre cut by lowes and home depot that are off by 1/2 inch or more from what it's supposed to be.

Thanks for the tip! Do you think the existing finish on Ikea bookshelves is enough? Or should I use a polyvinyl finish on it?