Which plug wire do I clamp when using the timing light?

[keslerkaiyu]

I'm trying to check my timing but can't remember which plug wire to use the clamp on. Also the tick marks are really confusing. Where exactly is the 5 degrees mark? Is it to the left or right of the 10?

I'm not even sure if I'm doing this corrrectly because everything I read on here indicate I have to ground something. I have no clue what that is.

Any light on the subject is greatly appreciated.

 

[tenn-gsx]

#1!!!!!!!!!!!!!!!!!1

 

[fourreGsixty3]

Its 5* BTDC...to the left of the 0 mark. Also make sure the arrow on the clamp is pointing towards the spark plug.

And here is a nice walk through... Engine Timing