Actually the "Trem Lok" button locks the tremolo from going UP.
How it works is it slides between the pressure plate and tailpiece frame to block the vibrato from going sharp if a string breaks, disabling the floating feature but allowing the guitar to soldier on through the song/gig until the broken string can be fixed including downward travel for vibrato if needed.
What's funny is I wound up disabling mine on my Jaguar.....it's never needed it, and I still beat the bar like a red-headed stepchild on that guitar.Â