Drawing a line same length as previous line. I assume there is a default setting that I must have turned off some how.

Drawing a line same length as previous line. I assume there is a default setting that I must have turned off some how. I noticed that when I would draw a random line then the next line I would start to draw a little marker would pop up showing the length of the previous line and you could pick it and have 2 lines the same length. I found where you can pick the "Length" check box and make all lines same length but this was easier to use on the fly. Any ideas of what the setting is?