These were excellent for me to cover some imperfections on new furniture I had purchased with a Cherry/Walnut finish over natural wood. My furniture had a bare wood nick where the varnish didn't cover in a noticeable spot on the front, long thin lines from a scratch in the concave concours of the cabinet door molding in a less noticeable downward facing location, and some other imperfections. These very effectively helped me cover all very well. I wouldn't even notice these spots if they had come like this as natural wood has its own imperfections and I would have been content if it came like this out of the box. Remember, furniture markers like this are how small imperfections are fixed by furniture stores. They just have a larger set of about 30 colors to choose from. These seem to be a reasonable selection that you can use to find a close fit.
These are varnish markers, and work like varnish. They are meant to apply to bare wood, stay wet for a short bit, and can be easily wiped with a rag or napkin. If you rub too hard, like varnish, you can nearly rub your coat off right away. But it should soak into the bare wood more easily. So carefully use the marker to color in the bare wood scratches or imperfections, and it is okay if it touches the finished area slightly if it happens. Just wipe with a napkin trying to wipe only the finished area off and leaving the recessed scratch covered. In fact, it seems to be better to wipe the bare wood area a little after letting it soak in for a moment to even it out, somewhat like you might do with applying real varnish. After wiping away the excess, it works great. Start with a lighter cover to be safe, then move darker until you are happy. Work in small sections at a time so that you don't let the area you started dry too much before you get a chance to wipe off the excess that might have gotten on other areas or if it looks uneven. Of course if it looks perfect, just leave it alone. It really isn't hard to do and not very meticulous, but does take a steady hand and task lighting if you want to be very careful. I just moved a reading lamp to help focus on the area.
For natural wood, with wood grain, and especially for varnishes that are intended to be uneven, scratches nearly disappear once covered. Once colored in, you can barely tell a scratch from natural wood grain. Of course results will vary depending on orientation of scratch or nick, style of wood, style of varnishing, and color. For my natural wood hall chest with a cherry/walnut varnish with curves & molding, it fit very naturally. But for furniture with fake wood surfaces and especially with perfectly even coloring, there is no way it is going to completely blend in. However, regardless, you are sure to make it less noticeable than a bare wood spot or scratch.