You know those shoulder straps on your jackets? The ones with a button that you always thought were just neat adornments purely for decorative purposes?
They serve a purpose, and honestly I've been alive for 35 years and had no idea.
Yes, @Francheskahor6 figured it out.
Those straps come unbuttoned so you can slide your bag, purse, murse, etc. right on in, and snap it back so it NEVER MOVES.
Turns out, those straps have some historical significance as well. On old military uniforms, those snaps were used to keep packs, ammunition, or bayonets from sliding off the soldier's shoulder