Editing length between locators (distance)?

[h0lgr]

Hey folks.
I'm having trouble getting a precise value out of the distance tool between two locators.

Yes, I can definately move the upper locator and the value will change, but I'm having trouble making it very precise. I'd like to change the distance to exactly 2.10000. 
Any ideas? =/ I've been scouring the web, and coming up with nothing unfortunately.

[n8skow]

Not the most elegant solution, but how about creating a cube the dimension you want, moving it's axis to the bottom - snapping the cube to your bottom locator - and then snap the top locator to the height of the cube?

[h0lgr]

I guess so, how would I go about setting the cube dimension to exactly 2.1?

[n8skow]

You can type it right into the attribute editor.

[_sebastian_f]

i have to say for a lot of tasks i also use n8skow´s method. also with other primitives. the good thing there is, it´s i.e. easier if it´s not just a straight line and you can subdivide it if you need to know the center etc. but for completion i want to add one thing which is maybe good to know for this and some other situations. hope the image is enough otherwise let me know.