Oh forgot blocks and bracing.....
Except for balloon older 1900 - 1950 will have diagonal bracing at every corner. Top from the corner out to the floor. A good area to avoid.
And not sure when they started 48" fire blocks. But guaranteed for remodels if the walls got opened. Around here they were still doing K&T up to the mid seventies for some reason. I never liked those flex bits, and prefer, infact insist on opening the wall to drill if I can't get it from above or below.
Oh... for S&G I googled "Knob And Tube"...
This is funny!
http://www.dimensional.com/~jbettin/mess/knights.htm
