«UCAG» - 

GLITCH 1: (please note that this is now patched)
1. go to the boxes near the spawn areas
2. use the barrels to get on the boxes
3. use ur knife and look at the pillar's corner
4. sprint jump into that corner and u will be concealed
bonus: on bravo side, go on the box on the left and jump into that pillar and move closer to the inside of the pillar to fall down into the pillar next to the corner of the box(nice place to hide in quarantine)
GLITCH 2:
1. u must go to the roof of the building
2. go to the entrance of the window (outside)
3. jump on the entrance
4. and now jump onto the roof of the entrance to the roof (its confusing'')(another good place to hide in quarantine)