The strap is too loose. Tighten it up a bit.

带子太松了， 再勒一勒。

《新英汉大辞典》

The screw on the machine seems loose; you need to tighten it up.

这机器的螺丝钉松了，你要上紧。

youdao

Let's put the support bracket to the rack and tighten it up with proper screws.

我们把承重支架安到机架上，再用适当的螺丝把它拧紧。

youdao

"You don't want to go out there and really freeze because it will tighten up your muscles, " Khabie says.

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On Monday, the Federal Reserve and the Office of the Comptroller of the Currency, both bank regulators, slapped sanctions on JPMorgan for the trading loss and ordered it to tighten up its risk management procedures.

NPR: Jamie Dimon Will Get A Pay Cut After Trading Loss

For the same reason, it wants to tighten up licensing rules, to make sure that airlines operating in the EU are financially in good shape.

BBC: NEWS | Business | EU clamps down on airline fares