How to make a bifold door?

If you're handy use the existing door frames to create a bi-fold door. No expert here, just thinking about what I've seen people do with cabinets and doors, for instance, where inner panels are removed and are replaced with other materials, usually glass! So why not take out the glass and insert a panel of wood/plywood. Then cut the door in half lengthwise, finish the door in stain or paint, use piano hinges to join the two halves together, add your door hardware to open and close the door and rehang using the existing hinges on the door opening. You can find directions how to build your own bifold doors on the internet, here is one example: https://www.hunker.com/13401853/how-to-make-bifold-doors

One example here of how to build your own bookcase secret door (looks complicated to me!): https://iliketomakestuff.com/secret-door-bookcase/ There are kits you can purchase to make this kind of door, too. They're not inexpensive.

Hi there. What about using two narrow bookshelves (like from Ikea) and joining them together to create the bifold bookcase door? Here's a larger one, but you could just use smaller bookshelves. Neat idea, btw! https://www.manmadediy.com/2982-how-to-make-a-folding-secret-door-bookcase

Cheaper to buy a bifold door. Check out salvage shops, Habitat for Humanity restore, Homecenters sometimes have seconds.

https://www.hometalk.com/diy/build/doors-windows/hidden-bookcase-door-492805

https://www.hometalk.com/diy/living-room/furniture/invisidoor-hidden-bookcase-door-2492317

https://www.hometalk.com/diy/build/shelves/want-a-secret-passageway-in-your-home-41983084

https://www.hometalk.com/diy/living-room/furniture/diy-bookshelf-door-6463599