Any guesses as to

[up2specks]

Are they supposed to work best in sand, gravel, or mud?

I don't own one but, I would theorize, because of their design/weight/less aggressive profile, that unless this actual one is tweaked/modified, many factors would prevail. Boat size, wind conditions, bottom-composition, rode(anchor line/appropriate length for depth =eg.- 7 -10 times water depth). DSJ- I think that for this particular model = light/medium-size rig >light-medium winds > proper rode etc. Bottom composition would have to contain a certain level of aggressiveness(rocks best, weeds/mud ok, sand/gravel worst... mixed combinations(+-)?) Modifications would "up the ante" = heavier gauge metal, longer grab cleats, longer-length chain etc.) Your question parallels the famous question "what came 1st, the chicken or the egg"!

u2s

[DockShootinJack]

Just curious. Considering it looked like a box scrape I figured as it was pulled along it would load with material to the point to be heavy enough to stop the boat. In the bottomless muck and mud in the coastal deltas I would be afraid that anchor would sink out of sight and be as lost as that Oak Island treasure them folks have been after. Old machines, mechanisms and such have always intrigued me. The pursuit of the better mousetrap

[up2specks]

Hey, just thought of a neat mod = Add treble hooks in hopes of recovering lost gear! Then again...Jimmy Hoffa?

u2s

[DockShootinJack]

Looks very similar to what they use to drag for bodies