When the slates arrived we were busy with the soakaway so slight delay in getting started then the digger conked out again so while the battery charged Iain started marking out for the slates.
Iain put a half slate on first then a full slate over the top for the first row and to help me put them on he made a jig but holding the jig, the slate and the nail wasn't really too good for me.
Anyway at this point, I'd only put 8 slates on I decided they weren't straight.
Then using a chalk line Iain set off putting the first double row back on but it still wasn't right. The place Iain was measuring from was the fascia but it's not straight!
So we then measured from the ridge line down and found we were 10 mil adrift because of the fascia, off came the slates and now we are sure it's straight.