Every pair that makes 5, 10 or 20 — as a chart to learn from, a drill to check with, and printable sheets for the fridge door. Abacus students know these as the small and big friends.
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Read them, say them, cover one side and recall the other. Fluency with these pairs is what makes carrying and borrowing feel obvious later.
Ten quick gaps — type the number that completes each bond. Check when done; reshuffle and go again until it feels automatic.
What Western classrooms call number bonds, abacus training calls the small friends (pairs making 5) and big friends (pairs making 10) — and drills them until every carry is a single bead move. If your child is learning bonds at school, the abacus route makes them permanent.