Precisely calibrate a sketch without having to fully constraint it.

[zalexzperez]

As explained on the screenshot, users don't always want nor need to fully define their sketch. For example, when dealing with Spline drawings. In such cases, it would be nice to be able to temporarily group and lock the selected sketch lines but still be able to 'calibrate' the grouped vectors by dimensioning from a specific point to another, as an alternative to using the 'imprecise' scale tool. 

Another example of situation would be when importing an .svg or .dxg logo and you just want to make sure that the design on it is not wider or taller than a certain value without having to use the scale tool to guess the appropiate scale factor.