Faster is correct: The tack collar or strap (I don't even know if there's an "official name", but it's like parrel beads in cloth form) is like a wide, fabric-covered belt with D-rings. It slides up and down the furled headsail as per the windspeed and whatever tension you have on the downhaul, which you would run through a properly sized block below it.
Depending on the point of sail and the windspeed, you can
rig a downhaul on a bowsprit or any reasonably secure attachment point forward of the forestay. I personally wouldn't recommend the eye strap you occasionally find on the forward top bar of the pulpit, but I've seen that on some boats.
If you have a constant light wind from a particular direction, tensioning and releasing the tack downhaul on an assym.
spinnaker is quite instructive, because you can easily discern the "sweet spots" that produce the most lift and thrust, and you can understand how too much or too little tension will stress the sail or get it out of that sweet spot.