From: Rabbi Moshe Sofer
To: Rabbi Moshe
Two travel merchants had an agreement to share profits under merchant custom, but when one proposed extending the partnership to cover hides purchased at the market, the other demanded compensation for his labor. The Chasam Sofer rules unequivocally for the purchaser: either the other party has no claim to the hides at all, or he must pay fair compensation for the purchaser's labor, as no valid partnership was formed for the market transaction and merchant custom does not extend to it.
Source: Shu"t Chasam Sofer CM §96