Take 20

Taking 20 represents taking as long as is necessary to complete a task. It allows a character to assume they have rolled a 20. It is essentially rolling the d20 enough times to get a 20, but without actually rolling - as this will normally take twenty rolls, taking 20 takes twenty times as long as a normal check of the same type.

If a roll of a 20 is not good enough to make the check, it naturally still fails. See Natural 20.

This can only be done when there is no penalty for failure of the skill check (picking a lock, deciphering a code) and when the character isn't under stress (such as being in combat).