When searching, remember, a few words are better than many
ID95-Commitment to Calling (Claiming) or Picking up a Discard (touch, move, lift)
Question: When am I committed to taking a tile I call for exposure?
Answer: You are committed to taking the call when you have either placed the discard on top of your rack (flat part) or have exposed tiles from your rack (sloped part) and placed them on top of your rack (flat part). You can change your mind if either of the two actions have not occurred.
Source: Mah Jongg Made Easy 2024 Edition, pg. 18, #13