Barber hones

A Barber hone is a cheap and easy way to keep your straight razors sharp for years with the right use if the edge stays undamaged.

Barber hones are synthetic stones that were used by barbers to do a quick touch up of the edge, thereof the name. They are usually small, suited for the barbers to keep in their pocket.They are typically thin/light as well, and good ones work exceptionally well at keeping a keen shave worthy edge, keen, and shave ready by merely making 2-3 passes across the hone every week or two.
The grit of a barber hone usually lies between 6K-12K depending on the maker, some hones are dual sided, with one coarse and one finisher side.

Barber hones are very hard, and do not need to be lapped very often, some claim that it is unnecessary to lap them at all.

There are probably hundreds of different barber hones available, most vintage but there are a few current makers as well.
Some that can be worth mentioning is:

Franz Swaty
Aloxite
Lithide
Keen Kutter
Champion

Pictures

Unknown brand

Franz Swaty

Skute hone

Size comparison of a barber hone next to the Norton 4K/8K

Inexpensive and the good ones, work quite well.
Fun and easy to use.

Can be in bad/poor condition, or worse yet, can be too coarse to work well. (Somewhat of a shot in the dark whether you'll get a good one or bad)
Very small, some can be tricky to use.

Because of their small size you will need to do x-pattern strokes when using a barber hone.
Barber hones can be either with water or lather or dry, this to ease the use.
Since barber hones are known to be fast, 5-10 strokes is usually enough to refresh a tugging edge, if the razor still isn't sharp enough repeat and try again.

Place the spine carefully on the hone, without the blade touching the stone, slowly lower the edge to the hone.
Adding no pressure slide the blade across the hone leading with the edge of the blade (opposite of when stropping)
When hitting the end of the hone, roll the razor on the spine to turn the blade to the opposite direction.
Remember to use X-stroke to make sure the entire length of the blade is covered.

See Honing for how to do the X-stroke.