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In the semiconductor industry and research, silicon wafers are transported in round plastic sample containers with a screw lid.

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Other than any other screw top though, the lid always opens (releases) when turning in the clockwise direction, as opposed to e.g. a bottle cap that opens counterclockwise.

Is there a practical reason for this? Why are they made like this even by different brands?

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  • $\begingroup$ Maybe the engineer behind this is left-handed ;) No I'm kidding but perhaps it's because it might prevent carelessness when opening the container (but I don't have proof of this but it's just my assumption). $\endgroup$ – user7211 Dec 22 '18 at 0:01
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Normally all lids are provided with right-hand thread. In those cases where a layman could accidentally turn the lid on, left-hand thread is used to prevent this. An example are threaded connections for gas bottles. Probally this is agreed in the SEMI standards.

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  • $\begingroup$ Left hand threads are used for gas so they are not connected to the wrong bottle - not a good idea to mix O2 and gas... the regulation control is different. $\endgroup$ – Solar Mike Jan 8 at 6:24

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