Agilent Technologies HP 16500 - Manual (Page 28)

5 Remove the screws connecting the interface module to the
mainframe.
Two screws through the top of the interface module connect it to the
sheetmetal plate, and four screws connect the rear plate of the interface
module to the rear panel of the mainframe (see the figure below).
Removing the Interface Module
Servicing the Interface Module
Removing and Replacing the HP 16500H Interface Module
3-11