When picking/cracking a combination lock a length of rope can be used to create a makeshift handle to give you a better grip of the lock. When the dials are moved or jumbled, the keyholes become dis-aligned and the toothed pin cannot be removed and is therefore locked in place. When correct code (in this case 9-2-4) is entered the keyholes of all the dials on the lock become aligned and toothed pin (second picture) can be inserted.
A combination lock (using a bike lock as an example as shown in the pictures above) has three or more dials with a keyhole through the centre of them.
