Sniper squat (how many units)?

I have a half wall that I want sniper to be able to stand up and snipe from but if they squat, I don't want their heads partially sticking up past the wall. Anybody know how many units that is?

 

Use the dev texture that shows the height of the player compared to the wall.
It's really helpful

 

what's the name of that texture in hammer? Is under tools/textures?

 

Put a model of a sniper in sniping position and a model of a squatting sniper on your map for reference? You can do that by just putting a prop entity with a world model as a sniper then change the animation sequence. Though apparently it will change all models to that certain animation.