If you want to fabricate a garden line with knots or marks every 75cm in the most efficient way with the least number of moves get someone else to make it for you....no kidding.

Measure your fingers - my 4th finger is exactly three inches long. When I stretch out my fingers, the measurement between the tips of my thumb and little finger is nine inches. I don't need a piece of string with knots in it.

Give a teenager £5 to do it for you ! I am told all the schoolchildren are now being taught metric measurements -
they havent a clue what 3 inches is. So its 75 cm.

That would be 75 mm, not cm!

Was going to say 75cm is nearly a yard!

Replied to your first question - ie mark your trowel.

Take a piece of heavy card measuring one and half inches wide or equivalent metric. Wind the line around the card, and spread it side by side. Then take a marker pen and draw a line along one edge over the string. Unwind and there you have it.

It's no good, I'm gonna have to ask, my curiosity has got the better of me - what on earth do you want one for, with measurements every 3 inches?

Shows how daft I am. Found a wartime recipe book in
British Heart Foundation shop, thrilled to bits to follow recipes in ounces.

I've got one of those Diane - don't try making the wartime marzipan out of soya flour and almond "flavouring" - it's dire - can't think why I liked it when I was small!