How to make a path square off a patio?

[KAgantua]

OK.
New patio.

I am building a new path running down the garden, off the patio, to the shed.
There is some flexiblity as to where the path can 'land' at the shed.

I want the path to be 'square' off the patio, not equal off my fence, or neighbours fence, or square off the shed, reason being they are all different angles, and if I do it square off any of them, it will look odd.

But my question is thus:
How do you make a long path 'square' off another object, in this case a patio? Dont want to do it by eye as I am cack-eyed at the best of times. Ill build it then realise its pissed.

Help me here lads please

[DocJock]

mark where you want your first slab of the path.

Measure 3m along edge of patio and mark again.

4m from first mark and 5m from second mark. Where they intersect, connecting to first mark, will be square to the patio.

[KAgantua]

nice one knew something about triangles and numbers, looked on wikipedia https://en.wikipedia.org/wiki/Special_right_triang... but its written by autistics

[227bhp]

Called the 3 4 5 method, it can be 3 4 5 of anything, the bigger or closer it is to what you are trying to square off the more accurate it is.
Simple Geometry (Equilateral triangle).
The idiot who did nextdoor's patio did not know of this method, he laid it not square off the house, but in line with a not very square (in fact tapered) outer boundary wall. Shortly after, we came to put a fence between the two properties to find the patio had strayed into our garden! He had to come back and run a stone cutting saw down the full length of it making it tapered.
Looks like a right dog's nob.

[Collectingbrass]

There's a number of trainagles you can use for this and 5,12,13 works just as well, and as long as the measurements are in proportion you can use any real numbers, i.e. 900mm, 1200mm & 1500mm.

I would measure a 3,4,5 to get me a point near the patio and 5, 12, 13 to get me one further away. I wouldn't try and project the line much beyond the tip of the triangle you've created as this will magnify any errors you introduce - even a few mm in the base line would put you way off by the time you get 6m away and your eye will definitely see it when you've finished the path.

Finally I would peg it out with string lines and then have a brew. Come back to it with fresh eyes, and look at it from a first floor room if you can. Think twice cut once...