This guide will let you know how to make a trap door in Bloxburg.
The first thing you will have to do is to make a 1*5 blocks of basement, place a wall in it and a secret bookshelf door just next to it.
After that, add four placemats on the first shelf as shown in the image below.
Cover the empty area and secret door with cubes and place four crates on the placemats.
Now will need to apply the grass except the crates and apply any color to the crates to complete the trap door.