Agilent Technologies HP 1660E Series User Manual page 268

Logic Analyzer Reference
Probing
Connecting the Grabbers to the Probes
Connect the grabbers to the probe leads by slipping the connector at
the end of the probe onto the recessed pin located in the side of the
grabber. If you need to use grabbers for either the pod or the probe
grounds, connect the grabbers to the ground leads in the same manner.
Connecting Grabbers to Probes
268