Old-fashioned mounts allowed you to snap numbers and letters onto bars to write custom messages. Newer acrylic stamp mounts are clear and printed with a grid, so you can align letters and see how your message will look before you stamp. Magnetic or peel-and-stick clear mount letters can be reused again and again.
Rubber stamps by Martha Stewart Crafts are available at Michaels stores.
Transfer paper is excellent for precisely transferring designs. Place paper, coated-side down, on the surface you want to transfer the design to. Secure the design on top of the surface, and trace with a stylus. Remove the transfer paper, and a carbon copy of the design will be left behind.