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. 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.

All ranks of the Royal Australian Air Force (RAAF) are entitled to wear the blue garrison cap with appropriate cap badge as an optional item with General Purpose Uniform (GPU), Service Dress (SD) and Flying Dress (FD) uniforms. The piping of the garrison cap for air officers is light blue, the piping for all other ranks is solid blue.

The RAAF is the only branch of the Australian Defence Force entitled to wear garrison caps.

In the Canadian Armed Forces, the field service cap (French: calot de campagne) is defined by the Canadian Forces Dress Instructions as a "cloth folding or 'wedge cap'...Originally designed for wear during field operations and training, it may now also be worn as an undress cap with full and undress uniforms." The cap is worn as part of the undress uniform by students of Royal Military College of Canada, and as an optional item by all ranks of rifle regiments with ceremonial dress, mess dress, and service dress uniforms.

The field service cap was originally adopted army-wide in 1939, and replaced in 1943 by a khaki beret. The coloured field service cap was a variant permitted for private purchase and worn only when off duty. These were in the colours of the regiment or corps of the wearer.

For personnel who wear air force uniform, the blue wedge cap (French: calot) is authorized for wear with all orders of dress, save for the combat uniform. It is properly worn "on the right side of the head, centred front and back, with the front edge of the cap 2.5 centimetres (1 in) above the right eyebrow." Cap badges are worn on the left side, with the centre of the badge 6.5 centimetres (2+1⁄2 in) from the front of the cap centred between the flap and the top seam. The cap worn by general officers is embellished with silver piping. Air force military police in dress uniform wear a scarlet flash in the front of their wedge caps showing 1 centimetre (3⁄8 in). Air force members of Canadian Special Operations Forces Command wear a tan flash in the front of their wedge caps.

Prior to Unification in 1968, the Royal Canadian Air Force wore uniforms similar to those worn by the Royal Air Force, including a blue wedge cap. After 1968, the uniforms of the three services were replaced by a universal rifle-green uniform; the air force, however, was permitted to retain the wedge cap, although in rifle green instead of blue. With the advent of the Distinct Environmental Uniform, the blue wedge cap returned.

The wedge cap is also the official headdress of the Royal Canadian Air Force Association and the Royal Canadian Air Cadets.