My take on the silt screw.
I required a means of Belaying the line in a in a twisting passage without much in the way of rocks or wall projections. it did have a floor of deep ish mud/silt (geologists please feel free to wince at this description) so a silt screw was the way to go. I could have purchased a length of plastic pipe but found I had a good collection of old solar garden lights (broken).
So I fabricated this ,well OK I drilled a hole glued the two parts together and fitted a bit of string :-)
My lawn taking the part of a sump floor :-) they can be driven in as far as you are able.
You can add some weight to it (hollow) if you want (cement). So far they seem very successful although winter floods will be the true test.
Just my take on it make of it what you will as I know there are many ways of doing this.
You can buy new solar lights for a £1 although that maybe wasteful?