It is a zero ohm link.
In the old days of pcb assembly, a special machine was used to make links from wire, these were then inserted by hand, or a link inserter machine.
In more recent days, most pcb assembly is done by machine, the resistors & other similar components are 'bandoleered', (sp) fed into the machine on reels which then cuts, bends & inserts the component. Zero ohm links were produced in a resistor shape, so the same machine could insert the links.
These days, most circuit boards use surface mount components, so same principle, different machine, but the zero ohm links are still produced in surface mount packaging.