In the days before modern plumbing the Night Soil Man (shit carter) would pay weekly visits to one's home to collect the sewage receptacle (large metal can) and leave an empty one. This service was usually arranged by the local government authority (the council). As the can was large and heavy the shit carter would often place the can on his head, in order to take it back to the shit truck. To make this task more comfortable he would wear a padded hat. The hat would, over a short period of time, become very flat on top due to the weight of the load.
"Strewth mate, the surf today is as flat as a shit carters hat."
by Wasim Ranamadruta August 30, 2012