Dave Plowman wrote:

In article ,
The Natural Philosopher wrote:

Don't boher. it is only there to stop pressure build up blowing
slates/tiles off...


Whilst that may be one factor, it also stops any driven rain reaching the
rafters. And given it's a relatively new idea, how did they stop tiles
blowing off in the old days?




They used more nails. And they blew off :-)