He plans to 'thin' (out) the young carrots in the garden. [=to remove some of them so that there is more room between the remaining carrots]
His hair is a little 'thin' on top. = He's a little 'thin' on top. [=he does not have a lot of hair on the top of his head]
The bank's decision to raise rates could be 'the thin end of the wedge'. [=many other banks may also decide to raise rates]
(..) They are used to keep secrets. It's da Vinci's design. You write the information on a papyrus scroll... ...which is then rolled around a thin glass vial of vinegar. If you force it open, the vial breaks... ...vinegar dissolves papyrus... ...and your secret is lost forever. The only way (..)2006 The Da Vinci Code