A pipe is a component rather than a drawn line because it carries state: whether the line is flowing, in which direction, and whether it is in service. A flowing pipe animates a dashed line in the direction of flow. When the operating system asks for reduced motion, the line stands still and chevrons along it point the way the flow goes.
Each elbow enters from one edge and leaves through the centre, so two elbows form a corner.
Pipe segments stretch to fill their grid cell, so a run is built by placing segments on the page layout. Snapping to a grid keeps the connections aligned when the page is resized.