A large number of Czech clothes stores have signs featuring the English words "Second Hand."

You might assume a secondhand shop here would sell shabby, Communist-era clothing, but this isn't usually the case.

If you ever get the chance to explore the class photos of Czech who grew up in the 1980s, you'll notice that the majority of the students' T-shirts and sweatshirts feature English phrases and Western logos.

If you ever wondered where those clothes your mother donated to charity in the '70s ended up, it might have been here, a decade later.

Under Communism, secondhand was a necessity for families raising children. Today, however, the stores offer a wider variety of used and even new garments, and sometimes carry genuine brand names.

Western European countries such as Germany and the Netherlands have strict regulations on the production of clothing, and any irregular garments are rejected and exported to places like the Czech Republic.

It's rare to find Czech-made clothing in Czech secondhand shops.

P.S.
When people have old but useable clothing they want to discard of, they often set the garments out by their rubbish bins, where those in need will find and take them. Alternatively, you can take old clothes to a dedicated Potex recycling bin.

UPDATE
For genuine secondhand clothing (and other items), try the Prague Thrift Store (Šumavská 29, Prague 2).