The 12/12 roof pitch is a tough roof to walk on. If you are a homeowner, I would not suggest even attempting to walk on a roof like this without some solid roofing shoes and experience.
What is a 12/12 Roof Pitch?
When you are talking about roof pitches, the first number is the number of inches the roof rises every 12 inches.
The angle on a 12/12 roof is 45 degrees.
Think about this when you are talking about the steepness of a roof. A roof with a 4/12 pitch has a much lower slope than a roof with an 9/12 pitch.
Photo Examples of a 12/12 Roof Pitch

12/12 Roof Pitch Multiplier
When you are measuring your roof, you must always take into consideration the pitch of the roof when estimating for materials.
A 12/12 pitch roof uses a multiplier of 1.4142.
Don’t forget to account for a waste factor as well when you are estimating.