[Nick Heath]

These are ok for an unloaded kayak or canoe on hard surfaces, but not loaded boats.  The wheels go under one end, so your arms carry most of the hull weight, unlike the bigger wheel sets that are near the balance point and so take most of the load.

For a day trip, they might be easier to use than a shoulder carry.

They could also be strapped on for unloading a boat from a vehicle where one end could otherwise drag on the roadway.