knobbed rigid shaft 326 function as a one way latch assuring an adequate compression force regardless of the blood vessel wall thickness referring to fig2 b the internal opening 384 of second sealing element 330 have two flat surfaces 390 on opposite sides of the internal opening 384 that interface with flat surfaces 368 370 of knobbed rigid shaft 326 to provide rotational stability of the seal assembly components 328 330 thus assuring that the sloped distally facing surface 382 and the fully deployed outer floating foot 328 remain parallel with the distal section 340 of the first sealing element 322 and the proximal or top surface 350 in particular the outer floating element 328 is illustrated in detail in fig2 a 24b the outer floating element 328 is generally rectangularly shaped and has a rectangularly shaped central aperture 400 and two protrusions 402 that extend from the longest side walls 404 into the aperture 400 the outer floating element 328 has a top surface 406 and a bottom surface 408 which are generally parallel to one another the protrusions 402 are configured to engage and allow the outer floating element 328 to travel along the knobbed rigid shaft 326 in the grooves 372 the protrusions are somewhat tear drop shaped but have two flat surfaces a first flat surface 410 and a second flat surface 412 the outer floating element 328 also has two inclined surfaces 414 and 416 one at either end of the outer floating element 328 and defines the ends of the aperture 400 the first flat surface 410 is at an angle u03b2 relative to the top and bottom surfaces 406 408 of outer floating element 328 see.