Vault Stitch is also known as Fan Vaulting and Church Roof Stitch. No Swedish name has been found. Let me know if you have any other names for this stitch.
I discovered it in Mary Thomas's Dictionary of Embroidery Stitches, where it is worked in the order of the purple stitch:
This way a LOT of thread is needed.
With yellow thread I changed the stitching to save thread.
Compare the back:
Once you have got the rhythm, you will get 'hooked' and work the stitches fast.
This is what it looks on my Aida sampler:
Fill this square with orange and yellow Vault Stitch.