If you need to, you can add a third bobby pin on top of your shoulder to keep the straps from moving around. However, this bobby pin will be more noticeable than the other 2, so it’s not great for lighter-colored tank tops. [2] X Research source
You can also do this hack with a safety pin, paper clip, or plastic bra clip.
To make sure your straps are really secure, try using this hack with safety pins.
If your bra is convertible, unhook the straps in the front and wrap them around the band before using bobby pins to keep them in place. [5] X Research source