The water-erasable marking pen from Prym is especially useful for tracing markings, which must not be visible, once the patchwork, quilting, sewing or embroidery has been finished.
The trick marker is a water-erasable felt-tip pen, available in white (for dark fabrics); it should be stored vertically, with the cap downwards, in order to prevent it drying out.
Important: Before using the marking pen, use it to mark a test piece of fabric and then test the removal of the marks from that piece of fabric.