Dell P2720DC Service Manual page 5

Wedge your fingers between the rear cover and
the middle bezel on the corners of the top side of
the monitor to release the rear cover, then use
S5
Scraper
to separate the rear cover in the below 3direction
of the arrow.
S6
Tear off the tape and cable to separate the rear
cover.
(No.1~2 Screw size=M3x4, Torque: 3± 0.5kgf.cm)
5