CHECK is guiding frame that is actively compared to your environment, whatever it is. It evaluates your sensual material for matches to its frame.
The operation of CHECK itself can by further detailed by subcode.
EXAMPLE:
CHECK: faces
ROAM your focus
WHEN you focus on a face:
HOLD your focus
CONSIDER face: expression
OBSERVE thoughts
ASSOCIATE thoughts with words
Here, the faces form the basic guiding frame. When they lead to you focusing on a single face, a suboperation is engaged.
Note that the CHECK does not have to be literal. It makes no difference to it (unless otherwise specified) whether your findings are conventional.
EXAMPLE:
WHILE: listening to music
CHECK: worms
This code is likely lead to rather associative worms.