I use the knot that follows: I can't find a name for it - in the Ashley Book Of Knots it's just
#1029, but you could call it a tucked honda knot. It doesn't slip, and doesn't seem to lock
up, either. Plus it will hold well without the final step (pic #3) so with that final step, you
can leave a very short, neat end without fear of it coming undone.
The structure forces it into a very round loop (which is why cowboys use the honda knot for
lariats).
It's good for semi-permanent attachments, but it takes too long to tie if you undo it every time.
First, make an overhand knot and pass the end through the tape loop on the tarp.
Put the working end through the gap in the 'pretzel' nearest to the tarp. Note that the end
came up when the overhand knot was made and goes under and comes up again this
time.
Continue over all the strands, then go back under the knot and come up through the gap in
the 'pretzel' nearest to you.
You can't just pull it tight, you have to work it tight (which is why it isn't good if you tie and
untie your guy every time)
But it looks quite good and is completely safe and relatively easy to untie when it's done.
And you can use it to peg the tarp directly to the ground if you want.