Abstract: A method for use by buyers and sellers in the execution of trades. The price of each executed trade within the system is logged. Next, a trend line is derived from the logged trades. The trading fee for a particular trade is determined based on the difference between the trade's price and the trend line as well as the size of the trade. This fee is imposed upon the buyer if the price of the trade is below the trend line, or imposed upon the seller if the price of the trade is above the trend line. The market markers in each item are evaluated according to how narrow their spreads were at the time of each transaction, and receive periodic bonuses based on these evaluations. A “crisis fee” is imposed on trades in the system when particularly measured qualities exceed normal bounds.

Abstract: Mating fasteners having a convex receiving surface and a concave inserting surface rotationally symmetrical about an insertion axis. A key code of annular projections and grooves is located in a plane normal to and concentric with the insertion axis. A locking mechanism engages the mating pieces only when in mating relation as determined by the key code. A planar embodiment is included. Easy and accurate assembly or connection becomes much less critical.