Weidmüller 1609060000 ZTA 2 ZDU4 Test Adapter – 9A, 250V, Black, for Z-Series Terminal Blocks

The 1609060000 (ZTA 2 ZDU4) is a plug-in test adapter used with Weidmüller ZDU 4 and ZTR 4 tension-clamp terminal blocks. As seen in your image, it features a red sliding lever (snap-in peg) on the side, which locks the adapter securely into the terminal's cross-connection (jumper) slot. This allows for a "hands-free" electrical connection for your multimeter or test leads while the system is powered.