Used for sealing notes and envelopes with sealing wax. The name of a seal has to be unique within the game. It uses 5 grams of sealing wax for every sealed note/envelope. For notes, the name of the seal is visible below its content. For envelopes, the name of the seal is visible when you try to see notes inside and you can't see the content without breaking it. Multiple seals for the same object are allowed.
Warning! Currently the project start page mentions: "Please be aware that afterwards the name can only be changed by using one of the sign altering tools (a chisel, a carving knife or a paintbrush), so be sure to check you have it just the way you wanted before adding resources to the project." This is not true, once the seal is made the name cannot be changed.