The heating fixture (clamped in the vise) doubles as holding fixture for the sample transfer from the heat treatment barrel (left) to the test barrel (right).

The barrels are aligned relative to each other via the cone pressing the heat treat barrel against the test barrel (seen at the bottom of the picture).

The threads on the heat treatment barrel (left) and test barrel (right) are aligned for smooth sample transfer.

The sample is 'threaded' from the heat treatment barrel (bottom) to the test barrel (top).