The hammer block and shank is the top part or “handle”of the hammer. It has a pivot from where it swings, it has holes where magnets can be pushed in, it has a long Shang at the end of which the hammer head is attached.
All of the hammer block and shanks are identical.
When orienting the hammer block and shank on the bed, it is best oriented upside down, that is with block at the bottom and the shank pointing up. The top face of the block is flat to give a large flat surcease area to adhere to the print bed, but even so it is strongly recommended that you add an adhesion raft in your slicer. This is because the shank is quite long, and without good adhesion, the part is easily dislodged as the printer head drags against the end of the shank as the torque increases as the shank grows.
There is no need to add supports. In fact, if you do, these can block up the pivot hole.
The default 20% infill works well.