By Brainpicker
United Kingdom 
thanks to those who responded to my query relating to sweet gem lettuce. I always believe in doing jobs in the most efficient manner and for along while had need of a garden line with knots/markings every 3"/75cm. one evening when I have nothing better to do I will tie one.
Unless of course some out there can tell me where I can
obtain such a thing. Business opportunity for someone??
13 Jan, 2016
Answers
Hi, I agree with Steragram, if you mean to use the string for planting out purposes, the 3" measure is only a rough guide, given based on the eventual spread of the plant, ie, a 3" planting distance would be based on a small plant, which would only spread about 1 1/2" before meeting up with the plant next to it, which would also have spread 1 !/2", there isn't much in gardening that has to be an exact measurement, Derek.
14 Jan, 2016
Why not just mark your trowel? Its already divided in two by the handle so it wouldn't take nearly as long as knotting string. I use mine as a rough measure.
14 Jan, 2016