Abdomen Out-lock
The uḍḍīyana bandha or abdomen lock is one of the standard locks which are required while doing breath infusion. It permits the yogi to control any generated energy in the abdominal region. The yogi compresses the energy to intensify and direct it as per directions given by the yoga-guru and/or the yoga texts like Hatha Yoga Pradipika.

In the advanced practice any such lock may be reversed. For instance there is the chin-to-throat lock which compresses energy which is in the neck or which approaches the neck from the trunk with intentions to pass through the neck into the head. The reverse of this lock which is to tilt the head back all the way is also practiced.
The reverse of the abdomen lock should be practiced with the regular perineum up-pull lock and the ashwini mudra anus sphincter muscle up-pull lock. Instead of contracting the abdomen inward and upward, the abdomen out-lock is one of pushing the abdomen outward but as soon as this is done the perineum up-pull and the anal lock are applied as usual.

The yogi should hold this abdomen out-lock firmly and should apply full attention checking to be sure that no energy leaks through the membrane of the abdomen, that all the infused breath and hormonal energy is properly contained.
If energy leaks that is the signal not to do this lock. It is the hint that one has not advanced in the practice enough to complete this practice. Then one should resume the usual uḍḍīyana bandha or abdomen lock and keep practicing with it for a time. Then again as advised one may attempt the higher practice.