4 squares at a time. Once you do this 4 times; flush.
I have never had a blocked head. (Where is the wood on which to knock?)
ISPA Yachtmaster Offshore Instructor Evaluator
Sail Canada Advanced Cruising Instructor
IYT Yachtmaster Coastal Instructor
ASA 201, 203, 204, 205, 206, 214
As I sail, I praise God, and care not. (Luke Foxe)