One of three options, the other two being Dashi nashi and Handashi. This is usually done for four-legged tana like Koko-dana.
Unlike the other two, this uses Yakan.
How to zendashi
Place the mizutsugi as usual for non-daisu (fully outside the tana, spout pointing toward the center of the mizusashi).
Pull out completely, 2h open lid (you’re sitting right in front), and replenish like normal for Yakan.
Pulling out the mizusashi
Your hands need to touch the tatami when taking the mizusashi for hakobi, but this is not true for tana.
It is much easier to handle if you take the mizusashi more from the front. Keeps your elbows from being weird.