They come in many forms. This looks flimsy compared to some with larger diameter 'bolt', but last time I used it I didn't even need a spanner on the nut- Just turning the wingnut was enough to persuade the top-race and bottom-cup home. (One at a time, not both at once). The holes in the blocks of hardwood are a loose fit on the thread. Small washer between the wood block and the nut at each end.
There's not much that can go wrong, once you understand that a cylinder of metal which is pressed into another cylinder of metal at an angle is an 'ovaliser', and to be avoided. You really shouldn't encounter that
much resistance- if
it's going in straight- not with a used headset on an old frame. Maybe there is more resistance with an unused headset on a new frame which has never had a headset installed before- I wouldn't know.