Dell 2400 - Figure 1-2. Opening the Latch on the 24-U Rack Door

1-4 Dell PowerEdge 2400 Systems Rack Installation Guide
Figure 1-2. Opening the Latch on the 24-U Rack Door
If you have a 42-U rack cabinet, slide the latch's push-button cover up as far as it
will go, press the push button, rotate the handle clockwise until the latch
releases, and then pull the door open (see Figure 1-3).