I have never seen anyone hide all the matzos. If this goes on in your house then yes I would lock them up to avoid this problem. Or do as I do…..I do not leave the dining room to wash. My children bring me the washing cup in a deep bowl so that i can wash at the table.
as to the shiur of hefsaik…….Shulchan Aruch Orech Chayim (166) The ramah says the time it takes to walk 22 amos.
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