What are these components in Arduino Mega Schematic? I was looking at Arduino Mega's reference schematic here and trying to understand how the circuit functions. However, I am unable to understand what these schematic symbols (marked in black rectangles) represent or what their function is. Can anyone please explain it to me?
The symbol indicates a pair of solder pads that can be bridged by the user using a blob of solder.

Here's something similar.



Figure 1. Source: CyberGibbons.