Is there an OS X application that overlays a grid onto the screen? When I am assessing the readability of scanned documents, I would like a transparent grid overlaid on top of my screen that shows perfectly parallel lines, as opposed to crudely "eyeballing" it. The lines of the grid should float on top of all other applications, and the holes of the grid should be transparent.

I do not need anything fancy, something like this (except rectangular, to fit my rMBP screen):



I have found a program entitled "GoldenMeanGrid," which is close to what I want, but its grid only contains two lines. This is a screenshot:



Does anyone know of a suitable program for my objective with an adjustable-sized grid? 

(2013 rMBP) -- (OS X 10.11.3)
The xScope app is a veritable powerhouse of overlay, measurement and screen detail functionality. 

You should be able to set up multiple grid lines if that is what you want. 


http://xscopeapp.com/guide#guides


This app has paid for itself tenfold over the years. Super useful for color and measurement and, of course, grids.