To fine tune a meter shunt with resistor wire or to adjust transmitter coil winding fine tuning can use this method.
Resistor wire is used in C shape able to slide through two terminals (lamps) to change length of resistance wire (where 1.12 ohm resistor represents piece of resistance wire.
This can be mounted on wood board and strip of paper with marking under the left end resistance wire to measure movement through screw down terminals (lamps). Vertical switches are contacts to circuit being tuned.
Resistance wire calculators can help choose resistance wire sizes.
http://www.jacobs-online.biz/nichrome/NichromeCalc.html
