The singing always started in the Derry except for Rangers vs Celtic when the singing section was in, what is now, the Copland Road end.
In the old Ibrox you could gauge the size of the crowd by how full the Celtic end was. Pretty empty and you were looking at 20,000 to 25,000. Semi full, and it was 30,000 to 40,000. Looking pretty full, it was 50,000 to 60,000. Packed, it was 80,000.
There was also an exit under the Derry which led to a path down to the bottom of Stairway 13 where you exited the ground. That was where I exited from on that fateful day 50 years ago.