Cinto is a very common way of saying cinto-de-segurança (seat belt). So, if you are not quite the wary kind of people, when in a car you may hear:
Põe o cinto! = Put the seat belt!
- Põe > gramm. 2nd person singular imperative (informal/spoken)
- Ponha > gramm. 3rd person singular imperative (formal/written/advertising)
Although we use the grammatical 3rd person você(s) for you(all), informal/spoken word uses the grammatical 2nd person for imperatives and object pronouns.
- Eu te dei um beijo = I gave you a kiss
- Eu lhe dei um beijo = I gave him/her a kiss ; I gave you a kiss (formal/written)
So you're probably asking yourself "This 2nd person cases happen in the regions they use tu". Wrong. Although tu has fallen in many regions, it left remnants in our everyday language.