Corners have rubber loops to attach to pegs/poles.
Covers the rectangular footprint of the inner tent. 130cm x 205cm.
Having got the Tyvek, and made up some footprints, I'm going to see if they sell cut to size and made up with the corner loops - they're also easier to ship than a folded length of the 2.8-m-wide tyvek sheet for a DIY version.
The red printing that's on one side of the Tyvek will differ from these pictures, as the first picture is of my own first footprint. The loops are now a little smaller, and the attachment tape thinner - current details shown in the third photo, and are like those of the Hilleberg Akto/Enan hexagonal footprint listed too.