There is a photo of a ground anchor (holdfast) on Phillip's No.9 restoration thread, just posted.
http://www.mapleleafup.net/forums/sh...ad.php?t=22324
The spikes were pointed hex or octagonal bar with a loop near the top to aid removal. I've seen various designs, but all have some method of removal welded near the top. There are some in the background of Phillip's image, rusted & standing up.
Mike