The period marked by the wholesale destruction of the functional zone of the endometrium is

Endometrial ablation (If you are asking what it is)
I don’t know what “period” it is if that’s what your asking (because ive never heard of that)

If it's a smaller child or infant, place one on the middle of the chest and on the child's back. (if it is a bigger child with enough room for two, place one on the upper right/your left of the chest, and one on the lower left/your right) the pads should never touch each other.