'floating the quilt top' just means to not attach the top itself to the bar that normally holds it... a lot of quilters (like me) just prefer to have final control over the top placement... if we have to 'cheat' one of the lines straight (piecing error) or if we are doing trapunto and want to add extra batting in specific areas, or if we just want a bit more 'puff' to the top... the tension on the top is much less and so produces all these possibilities, as well as the 'getting to the batting to smooth out wrinkles, and 'picking threads' that were mentioned before. all good reasons to float the top and if you want to see someone demo it... sharon schamber on youtube, does a great 'loading, unloading, floating, rice bag, just plain general 'setting up' video...