How do white blood cells move when outside of the blood stream

Scientists have shown that rather than inching along blood vessel walls to reach injured tissue, white blood cells sprout hundreds of "legs" that grip the vessel walls and propel them, millipede-like, to the proper site. Illustration of a white blood cell flowing in the bloodstream with red blood cells.

White blood cells use "legs" to grab ahold of the blood vessel walls to inch their way forward.