There is a scratch on your table you no longer see. It happened during a move, or a chair went back too fast, and for a week it was the first thing you looked at. Now it is furniture. You would still rather it was not there.

The reason it catches your eye at all is colour, not depth. A scratch in a finished surface is a groove where the stain has been cut through to lighter wood underneath, and light hits that pale line differently to everything around it. Depth is why you can feel it. Colour is why you can see it from the doorway. Those are two different problems and almost everything sold for this fixes only one.

A set of markers and wax sticks fixes the colour one. The marker lays pigment into the groove so the pale line stops reading as a line, and the wax fills the shallow ones so the light stops catching an edge. Thirteen shades exist because wood is not one brown, and a near match at arm's length beats a perfect match you cannot buy for the specific oak in your kitchen.

The trick is to start too light. You can go over a repair again and darken it. You cannot lift colour back out once the wood has taken it, and a scratch repaired two shades too dark is more visible than the scratch was. Test on the underside first, every time.

Here is the limit. This is cosmetic and it is meant to be. It does not rebuild anything. A gouge deep enough to catch a fingernail hard, a corner that has lost a chip, a veneer that has lifted: colouring those in gives you a dark mark in the shape of the damage, which is not an improvement.

It is also weak on anything that is not really wood. Modern furniture is mostly a photograph of wood laminated onto board. Where that print has worn through, there is no grain underneath for the pigment to sit in and the repair reads as a smudge.

And it is not permanent on a surface that gets used. A repaired scratch on a dining table takes cleaning and heat, and you will go over it again.