Shovel blade and zip: what they have in common

1. Step 1. Shovel blade — is part of — Shovel. A steel plate that cuts into the ground.
2. Step 2. Shovel — uses — Wedge. The blade enters the ground like a wedge.
3. Step 3. Wedge — is part of — Zip. The slider works like a wedge, bringing the teeth together and pushing them apart.

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