Parcour, or free running, is a sport in which traucers treat all barriers as insignificant, and use them to launch themselves further on. To get over barriers such as walls or rails, they have devised a set of vaults. One of the most impressive is a monkey vault.
A wall or other object like it (rail, bin,...) that is just above waist hight.
Persistance
Step1
Run up to the object you are vaulting at a steady pace. You will soon learn how fast or slow you need to go to make the vault. Look where you will place your hands on the wall.
Step2
place your hands on the object, spaced reasonably apart.
Step3
This is the hard part: you have to almost jump and tuck your feet in, but letting your arms do the work. Once your feet have became parallel with your arms, you have to "let go" of the wall, by pulling your arms up so they are in the air.
Step4
Land and continue running.
Tips & Warnings
Don't be afraid of clipping your feet on the wall, as you are much more likely to make it than to clip your feet, and most of the time your feet will just flex anyway, allowing you to carry on with the vault.
Parcour is dangerous, sometimes fatal if taken to the professional extremes. Always be aware of the risks you are taking.
People don't tend to be happy when you destroy their stuff, so don't do anything that could cause damage to their property.