Whetstones
Norton Waterstones
This Norton 4k/8k stone is an excellent whetstone to sharpen straight razors; I mainly use the 4000/8000 combination, moving from the coarser the finer
side. I come with instructions.
An advertorial site about the use and maintenance of razors, and of whetstones for straight razors:
https://www.gentlemansgazette.com/straight-razor-shaving-guide/