Asus AP1720-E1 - Manual (Page 36)

2-10 Chapter 2: Hardware information
11. Press down the fan and air tunnel
assembly until the side rails slide
past the grooves and over the rail
stoppers. The protruding tab on
each corner of the air tunnel
should snap over the dents on the
retention mechanism.
12. Connect the fan cable to the fan
connector on the motherboard.
Fan cable
Fan connector
Rail stopper
Side rail
Protruding tabs