It says in Shabbos (12a) that one should always check his pockets on Friday so he won't accidentally carry on Shabbos.
I don't understand the purpose of this checking. Even if one did carry unintentionally, he would have been a Misasek which is Pattur (and possibly Muttar). According to Rava, who says that we don't make a Gezeira LeGezeira (11b), why check one's pockets?