The paper edition.

Make room for the unfinished bit.

The dotted rectangle is the card edge. Cut there if you want small cards, or carry a whole sheet in a folder. Do not fold through a grid: a crease can make a lightly pencilled number hard to read.

The second sheet includes a reminder card and a “where I left off” slip. Put the puzzle number and your last certain step on the slip, then keep it with the unfinished card in an envelope. The answer key belongs in a different pocket.

Choose a pause that fits.

A number trail needs a stable surface and enough room for your hand. Sitting at a table is a better fit than standing in a crowded queue. If you only have a few minutes, look for one forced move and stop there; finishing the whole trail is optional.

A 4 × 4 grid gives you fewer squares to revisit. The 6 × 6 grids offer a longer path, but more printed clues can make sections easier. Choose by the amount of paper you want to work with, rather than a promised completion time.

Use the pencil and bag you already have. If the card bends, change its envelope or add a backing card before adding more activities.

A quiet session, with room to choose.

For two people, make two copies of the same puzzle. One person may want silence while the other prefers to compare a turn. Agree to ask before revealing a clue. A helpful prompt is “Which numbers touch this square?” rather than reading the answer key aloud.

For a small group, put the 4 × 4, 5 × 5 and 6 × 6 cards in separate piles. Keep a spare pencil, an uncut sheet and the answer key available. Offer a place to leave an unfinished card. There is no need for a leaderboard, signup or personal details.