Construction Lines....Again!

 From:  DannyT (DANTAS)
3847.1 
Hi Michael,

I was dragging items around while modelling and snapping the items to other object ends, mid etc. then I wanted something to line up at an intersection of two separate edges, and thought would it be possible to bring up some construction lines before dragging stuff around........or can I do that now ?

Just a thought
~Danny~