Describe how Sujud Qabli is performed.

Sujud al-Qabli is the prostration of forgetfulness (part of Sujud as-Sahw) performed before the final salutation (taslim) to make up for a deficiency, forgetfulness or doubt that occurs during the prescribed prayer (Salat). It is performed as follows:

1. The worshipper completes the prayer up to the final sitting and recites the tashahhud (and the prayer upon the Prophet).
2. Before making the closing salam, and while still sitting, he says "Allahu Akbar" and goes down into the first prostration (sujud), just as in the normal prayer, praising Allah (Subhana Rabbiyal-A‘la).
3. He raises his head saying "Allahu Akbar" and sits between the two prostrations for a moment.
4. He says "Allahu Akbar" again and performs the second prostration in the same manner.
5. He raises his head, sits, and then makes the final taslim to the right and to the left, thus ending the prayer.

When it is done: the qabli (before-salam) prostration is generally made when the worshipper has omitted something, such as forgetting the first tashahhud, or when he is in doubt and builds upon the lesser (certain) number of rak‘ahs. It compensates for the shortcoming and completes the prayer, in accordance with the practice of the Prophet (S.A.W.).