A side cap is a military cap that can be folded flat when not being worn. It is also known as a garrison cap or flight cap in the United States, wedge cap in Canada, or field service cap in the United Kingdom; or in vulgar slang as a cunt cap. In form the side cap is comparable to the glengarry, a folding version of the Scottish military bonnet. It has been associated with various military forces since the middle of the 19th century, as well as various civilian organizations.

The Glengarry bonnet is a traditional Scots cap made of thick-milled woollen material, decorated with a toorie on top, frequently a rosette cockade on the left side, and ribbons hanging behind. It is normally worn as part of Scottish military or civilian Highland dress, either formal or informal, as an alternative to the Balmoral bonnet or Tam o' Shanter.