Trimble Outdoors SPSX51 - Manual (Page 58)

5 Setting up the Receiver
56 SPSx51 Modular GPS Receivers User Guide
11. Replace the rubber endcaps.
12. Place the black cradle on the black base plate. This places the SPS551H GPS
receiver on top of the SPSx51 GPS receiver.
13. Make sure that the display is facing in the same direction on both receivers.
14. Prepare the eight nuts, spring washers, and flat washers.