CISTRSC (pronounced Sister-Sea) is a mnemonic used by some Canadian glider pilots to remember the sequence of actions required before take-off.
[1] This preflight check was developed by the Royal Canadian Air Cadets for use on the Schweizer 2-33 training glider.
The check is not applicable to other glider types that are more complex than the 2-33 and include features such as flaps.
Like all mnemonics this check has become part of aviation culture and folklore.
[1]