The Bomb Hole? That goes back to when I started, where out of the corner of your left eye you could see the traffic on the A11 racing you as you "tore" (on a Bantam!!) down the Norwich Straight. I never understood why the circuit was altered, unless it was for H&S reasons for marshalla at the hairpin - on one occassion I was marshalling there and saw a colleague jump into the air so that a riderless and on-its-side machine didn't take him off at the ankles, bouncing back harmlessly from the bank! The Bomb Hole sure was a challenge, and getting it right made a big difference to your entry speed to Coram Curve and through the start/finish (no Mickey-Mouse Russells either).
Again, I don't know about road markings nowadays, but there were many places to be wary of in the 70s, especially in the wet. If you kept off the white line coming out of Kirkmichael you were risking crossing the manhole cover - both were really slippy.
In response to an earlier comment about 'K' in Quarry Bends - yes, that was when they were bends and before the lap time was reduced by around five seconds by straightening them!
Most of this, and all other discussions here will be redundant soon anyway, as IMHO what keeps the TT going is its sense of history, and as the new masters are doing away with Parade Laps and the like, the end is nigh.