Ruler/Protractor tool - change snapping values for easier snapping to vertices? I wanted to use the Ruler/Protractor tool to measure some length for an environment scene.

Is there a way to change the snapping values of the Ruler/Protractor tool?
or is there a way to easily snap one side of teh ruler to a selected vertice?

when I try to use the Ctrl+Drag, the snapping wanders of the vertice which I want it to snap to, which is really frustrating.

EDIT;
using the tool while in edit mode, this is often the result.
If you only want to measure simlpe edges I would use the Mesh Display Tools in the Propertys Panel of 3D View.(Press N to diplay)

First switch to edit mode. Then activate Edge Info>Length:


Then it displays the the length of the selected edge or what else you want in the 3D View.