These pencils are used to color white cut edges that appear when printing paper is cut. Applying color to these edges gives paper models a cleaner and more polished finish.
One point to note compared to markers is that you need to apply a little more pressure with pencils to get the color to stick. This can sometimes cause the paper to tear or the surface to peel off.
Some types of printing paper have a coating that enhances surface colors. On such paper, the color applied to cut edges may appear darker than the surrounding surface. For this reason, it is recommended to use colors slightly lighter than the surface colors.
This page introduces Shuttle Art products as an example. They are inexpensive and available in a wide variety of colors. However, according to product reviews, some items may be defective, so please be careful when purchasing.
Please refer to the website links for detailed features and pricing information.

Product Data
Website: Product Page, Amazon
Brand: Shuttle Art