Anne Lamott suggests an index card, and I have used these, but they suggest something pre-planned, organised. The envelope, especially if it has an address with a stamp or franking mark, is open to all kinds of improvisation. It knows it is inexpensive and thus prompts writing that is (almost) afraid of its own voice. The envelope has no ideas above its station. The low-stakes setting is ideal for getting some real work done. A sketch of an idea. The first line of something. The whisper of a voice overheard on the street. Or you might use it to scrawl a phone number, an email, or the name of a book. Its nature as an already used artefact reflects the impermanence, the provisionality, of all writing. Paradoxically, this invites creativity, the loosening of inhibitions, freedom. Somehow the envelope knows this and is welcoming of it. Somehow the envelope brings hope.