Breadboards and accessories are used for testing and prototyping small electronic circuits. Electronic breadboards are plastic blocks that have a pattern of holes into which experimenters can insert electronic components, mounts, and connectors. Solderless breadboards (SBBs) have spring clips under the holes in the plastic to hold electrical contacts. A breadboard circuit on a solderless breadboard can be modified easily. A solderless breadboard can be mounted on a plate or case with other accessories. Two major types of breadboards are surface mount (SMT) and Manhattan-style. Breadboard accessories include wiring kits, connectors, pins, spacers, wire insertion tools, test sockets, test probe tips, card racks, power supplies, and pulse generators.