Measuring

I'm having a hard time finding any kind of background reference measuring grid. Say I have a figure that needs to crouch down to clear a 3'6 opening, I can't find how to reference 3'6 in the Daz work space to know how to pose my figure accordingly. After spending too much time looking for answers, I found that someone imports a background "measuring wall" scene. Thinking, surely that's not how it's done, there has to be an actual measurment system within DAZ, I went ahead and down loaded the "measuring wall" and spent another hour trying to figure out how to load that into the scene... I finally gave up on that too and came here to ask where I can find the actual proper way to measure within DAZ. Thanks.
Comments
https://www.daz3d.com/measure-metrics-for-daz-studio will give you tools for direct measurement. You can also just make a plane and move it up 3'6" covnerted to cm - that's 42", so about 105cm. Al translation sliders in DS work in cm.