This cuff is useful as what I call a "second column" tie -- for a situation where you've already got something attached to your rope, and want to now attach the line to a single column, while the standing part is under tension.
To start, make a slipped overhand knot in the standing part, such that the working end (not the side already tied off) can slip through to enlarge the loop:
Now take the working end around your column, and through the loop:
The nice thing about this tie is that once you get to this point, just hanging on to the working end will support the column / maintain the tension. Ignore the knot where the rope changes color -- that's just to make the lines contrast so that it's easier to see what's going on.
Next, you want to adjust the loop so that it ends just a little bit above the top of the column, by pulling rope through the knot to elongate (or, if necessary, shorten) it; this is also your last chance to adjust the overall tension on the tie:
Now wrap the working end back around your column in the opposite direction:
Then through the loop:
Back around the column, reversing direction again:
Through the loop again, and so forth:
You can do this as many times at you like; the key thing to not getting tangled up is to add each wrap on alternating sides of the cuff, based on the natural position you're in after going through the loop.
When you feel like you've got enough wraps, after your last pass through the loop, just split the lines and tie a square knot:
Alternately, you could finish it with a couple half hitches about something; but I find it easier to keep the tension even on the last wrap when ending with a square knot.