When it's a 50
When it's NOT a 50
"Not the Whole Head" or "Half Head"
The whole of the paddler's head does not pass through the gate line.
Photo stolen from the judging guide produced by Canoe Slalom New Zealand
If a paddler or C2 crew would have incurred a 50 penalty by "not the whole head" the paddler/crew can return, make a second attempt at the gate and "clear" the 50, provided that they did not pass through the gate line in the wrong direction and they have not touched or negotiated a following gate.
But if there was a touch on any pass, the touch penalty stands.