Thanks for the help!
Drawing lines with out measuring would be a great help.
I have tried modifying an existing drawing, as is the case some times i have to change the drawing anyway, but some times i find it faster to redraw, I find a lot of bugs or behavior thats not expected in Sketchup.
How I normally draw, is start with a foot print in 2D, draw in the basics, Pull the walls up, work on the roof then snap it to the walls, What would be good would be a short cut that I can click, say 45mm, then 555mm then back to 45mm, as roof layouts require lots of work.

I have not had time yet to look at tools available.
I have found the Google Youtube videos of little help.
All of the drawings are simple in shape.
I will upload some Images later, when i have resized them
Thanks guys.

I use Sketchup Pro 8.

I am doing so many drawings now, almost every day.
They are not complex in a drawing sense, Simple Garden Office Studios.
Each Studio has variations in design, but basically they are the same. Only length and width change as well other structural engineering changes.
Such as wall heights, Panel widths, Beams and windows, Basically there is a Vast amount of repeated drawing, one example would be Tape, 45mm then 555mm over and over, same with the rest of the drawings, Its all Repetitive and takes time.
Can some one point me to a plugin or method that I can use for common tasks, I use all the time. Saving me a lot of time!
A ruler memory would be fantastic.

Many thanks
KN