An answer from my friend Jason who discovered this when he was a young believer many decades ago, regarding the Passover ceremony:
Got your message about the Passover. The pocket thing is called a matzoh-tosh (tosh or tasch being the German/Yiddish word for pocket). It has three compartments, and into each one is placed a whole sheet of matzoh. The middle one is taken out, broken in two, and half of it is hidden near the beginning of the ceremony. Towards the end, a child goes and looks for the broken piece and brings it back to the leader who checks to see if it matches and then it is returned to the middle matzoh.
Christians tend to feel that the tasch represents God (Father, Son, Spirit) and that the middle one is taken and broken and hidden away, then reunited and returned to the other two. I looked up what the Jews believe this means (which is hard to find since there are 40 million Christian sites about it) and found this:
"During the Passover Seder, three sheets of matzoh are placed on the table and covered with a cloth or “Matzoh Tasch”. My family’s explanation for the matzoh on the table was that they represent the castes of the Jews, the Kohanim, the Levites an the Israelites. During the Seder, the middle matzoh broken in half, one for use in the Service and the other for the Afikomen (dessert), which the leader hides.
After a child locates the hidden Afikomen, at the end of the dinner, and is properly rewarded, each participant at the Seder eats a small portion of it. This signifies the end of the Passover feast."