The wonders of electromagnetic wave physics. An approximation of a stretched parabola reflector dish. Works best if antenna is positioned in the focus of the parabola.
I genned up a redneck directional parabolic dish to boost my WiFi antenna using aluminum foil taped to the back side of an old umbrella. Used rubber band to hold antenna to umbrella pole in approximate focal area. It actually boosted the signal significantly, but very tricky to figure out optimum direction if you don’t know where the WiFi signal is coming from with multiple sources.
the umbrella could be held with only rubber band to the router?