Warning: only for boys. when you are in puberty what is an "arrection? "

It's called and "erection" and it is normal. It is when the blood flows to the penis because of hormones. It can come from arousal or unexpectedly, since during puberty your hormones are changing and there is a lot of change happening in the body.

Exactly, it's one of those things that happen when you first start puberty my friend.

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.