Chalk pencils by Hancock’s; just like tailors chalk but in a handy pencil format. Easier to use with rulers, and rubs off. Should wipe off/wash out easily, but always test on a small piece of your fabric first.
Hancocks Tailors Cloth Marking Pencils in Standard 7 inch and half length. The chalk marking material is protected by the wooden pencil covering and used in much the same way as conventional tailors chalk.