what is this "+" mark on B737 cockpit panel?

[PappyJ]

Build - built. Yep, you got me on that one!

[forget]

P.S. Tip: People casting aspersions on fellow PPRuNers' educations, should first check their spelling

Pssst. Pappy. You missed the 'educations', bit like sheeps, the dodgy use of a colon and the missing full stop.

[muduckace]

Pappy J is wrong on topic but correct about fuscelage index marks. They are more commonly used in heavy maintenance when the aircraft needs to be jacked and shored prior to removal of too many skins. The aircraft is measured with survey equiptment then checked again after the structural work is complete. MDC products use a large button head rivit.