Test tube and rope: what they have in common

1. Step 1. Test tube — is made of — Glass. Glass.
2. Step 2. Glass — is material for — Hourglass. Bulbs.
3. Step 3. Hourglass — is used in — Chip log. The time of a speed measurement was taken with an hourglass.
4. Step 4. Chip log — has part — Rope. On a line with knots.

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