When using a directional antenna, how might your station be able to communicate with a distant repeater if buildings or obstructions are blocking the direct line of sight path?
Why VHF and UHF signals reflect well off large flat surfaces like metal buildings, water towers and hillsides. If the direct line of sight is blocked, you can rotate a directional antenna away from the repeater and aim at a reflecting object, bouncing the signal around the obstruction. This is a common technique in cities, where you often hear yourself best pointing at a building rather than at the repeater itself.
Watch out Trying the long path applies to HF signals traveling the other way around the world via the ionosphere, not to local VHF/UHF repeater work. Changing polarization on VHF FM usually loses signal, since repeaters are almost always vertically polarized, and raising SWR only wastes power.
Blocked path? Point the beam at a big building and bounce the signal in.