We won't lie — this hack from @mishkashoe on Instagram ... Using the OXBERG doors, which are specially built to fit onto the BILLY bookcases, you are able to create closed storage — perfect ...

Take, for instance, these large pink IKEA BILLY bookcases that basically turn this studio into a one-bedroom, or this IKEA ...

but none are more prevalent than Billy bookcase hacks. They are everywhere. As I scrolled one night, it inspired me to build ...

Using a few IKEA Billy bookcases she bought off Craigslist, Nozawa created a faux built-in library for a total of $220, or one-fifth of what she would have spent if she wanted a real one.