A modern solderless breadboard consists of a perforated block of plastic with numerous tin plated phosphor bronze or nickel silver alloy spring clips under the perforations. The clips are often called tie points or contact points. The number of tie points is often given in the specification of the breadboard.
The spacing between the clips (lead pitch) is typically 0.1″ (2.54 mm). Integrated circuits (ICs) in dual in-line packages (DIPs) can be inserted to straddle the centerline of the block. Interconnecting wires and the leads of discrete components (such as capacitors, resistors, and inductors) can be inserted into the remaining free holes to complete the circuit. Where ICs are not used, discrete components and connecting wires may use any of the holes. Typically the spring clips are rated for 1 ampere at 5 volts and 0.333 amperes at 15 volts (5 watts).
Here's a half size clear breadboard with dimension 8.3cm x 5.5cm. It has two power rails on the sides to allow more than one power level. With a total of 400 tie in points, all pins are spaced by a standard 0.1"(2.54mm). It has a self-adhesive on the back and also interlocking parts, so you can hook as many together as you'd like.