question| How can a worshipper who has a valid and canonically recognized reason to perform his canonic prayers while sitting on a chair carry out his prostrations? Should he raise the turbah and place his forehead on it?
answer| If he is able to bend far enough to place his forehead on the turbah, he must carry out the prostration in as close a manner to the original format as possible. That is, he should place the palms of his hands on a fixed platform (such as a table) in front of him, bend over far enough to place his forehead on the turbah that is situated on the fixed platform, and position the tips of two large toes of his feet on the ground. Obviously, in this position the knees cannot be placed on solid ground, and therefore this condition of the prostration is inapplicable to worshippers performing their canonic prayers while seated on a chair.
 Turbah, referred to in Farsi as muhr, is the small clay tablet on which Shia believers generally place their forehead in performing the prostrations of the canonic prayers.