One of the standard laboratory methods of testing slip resistance Ð see also pendulum test. German DIN Standard 51097 classifies wet/barefoot conditions in classes A (shallow slope 12 - 18¼) to class C (slope >24¼). DIN 51130 classifies safety booted feet on an oiled surface. Classes range from R9 (6-10¼ slope) to R13 (slope >35¼)