For a few calibration procedures, a 2450-CAL-KIT accessory is required. This is accessory is not sold anymore, but it is simple to create, here's an FAQ that describes the fixture: https://www.tek.com/en/support/faqs/what-is-the-2450-cal-kit
Another question we frequently get with 2450 calibrations is if you can use the front panel. The front panel can be used for performance verification, but for making adjustments, the rear panel must be used.