Technically, the lightning bolt in the profile view is the glideslope intercept altitude (GSIA). It's the altitude you have to be at near where you're supposed to be at where you're guaranteed to capture the real glideslope. Above the glideslope, there are false glideslopes at angles of roughly 6 degrees (upside down), 9 degrees (rightside up), 12 degrees (upside down), etc...
Before you get to the GSIA point, you're not supposed to use the glideslope for vertical guidance. Most of us in bugsmashers without VNAV will do the "dive and drive" to each segment altitude. Airliners with FMS will have the FMS calculate a smooth descent profile that keeps them above the min segment altitudes.
GSIA usually occurs somewhere near the Non Precision FAF.
Oh, and ATC is not supposed to vector you to the FAC above the GS, (due to the false glideslopes up there), and on a vectors to final, the intercept point has to be outside the approach gate, which is either 5 miles away from the airport, or 1 mile outside the FAF/GSIA, whichever is farther.