There are different ways to attach a spring support to a rod.
For A-Type constants and variables, you need two separate rods. The top plate of the assembly includes a threaded piece that will connect to an upper rod. A second rod will be connected to the bottom by the spring’s threaded load column.
For B-Type and C-Type constants and variables, you need one rod to attach to the spring assembly’s threaded load column.
For D-Type and E-Type variables, a single rod runs from the bottom through the top of the spring and hex nuts are used to secure the rod in place.
For D-Type and E-Type constants, a single rod is attached using a turnbuckle.