This thing is a lifesaver! I'm 5'1 and the roof of my vehicle is taller than I am. The first few times I tried sliding my 48lb kayak on the roof were rough - I could get it up there, but it took several tries and was physically exhausting. I use the roller on the vertical back window of my hatchback and it gives me a much more manageable place to rest the front of the boat while I push it up on the roof. I'm able to get the boat up and down in one shot fairly easily now. The only downside is that it can take a little work to get the suction cups to grip (though when they do, they hold strong for me). I followed the advice of another reviewer and carry wet wipes that I can use to really thoroughly clean off the area of window before I try to stick these on and it usually works pretty well. I'm glad this solution is available - it's really increased my confidence in being able to take my kayak out by myself, knowing that I'll be able to get it on the car to go home even when my shoulders are tired from paddling.

I love this thing! I don't have a tall car, but I don't think I'd be able to manage my 10' kayak by myself without this. I'm completely comfortable going out alone with the help of this boat roller. The only reason I didn't give 5 stars is that it can be finicky - my back window has a slight curve, so if it's not in just the right spot, or if the window is dirty, it won't stick - sometimes it takes several tries. But a very good, solid product.

I use this to lift a 10 ft Fusion kayak that is 44 pounds up onto my Subaru Forester. I'm 5'4 and 103 pounds, so it was nearly impossible for me to load an unload by myself before this! While this does allow me to go out by myself, it is still very awkward for me to load and unload. If your kayak or canoe is more flat bottomed than don't worry, but mine is fairly angled so it slides around a lot no matter what action I'm doing, which is why I knocked it back a star. I wish the design was slightly more universal, maybe angled more sharply so the sides can keep the yak from sliding around so much? But again, this product does fully allow me to head out on the water alone, so I would recommend.

Very good equipment. I had a 60lb fishing boat that needs to load and unload to/from the top of my SUV. It is pretty hard for myself alone to do it, especially after long time paddling.
looked at most of the reviews, especially the bad ones. I was concerned it might not be able to suck on the window as my windows is curvy. after I received it, I can see the the two cups are designed to be flexible. as long as you push a little bit hard before turning the sucking action bar down, it stays on the window solid.
It does make the loading/unloading much easier. So far so good.

We bought the Sherpak for loading our two small (13-ft. x 25-inch), lightweight kayaks side by side on 2 Thule saddle-style kayak carriers atop our Subaru Forester. The suction cups are too large to fit on the top of the Forester's rear hatch or on the rear edge of the roof, so we attached them to the hatch's rear window. After the window glass was thoroughly cleaned, the suction cups gripped strongly with no slipping. The suction cups had to be positioned right to the edge of the glass. But even then the rollers were almost in the center of the car, several inches inboard of the saddle-style kayak racks. To load a kayak, we had to lift and position the its bow on the rollers, and angle the boat toward the side of the car in order to get push it forward in the saddle. This required one person to lift the boat, and another person to stand alongside the car to guide the boat on to the saddle and keep it from falling off the car or dropping on the car's roof.

Unfortunately, in one of the attempts to load a kayak on the car, my wife injured her wrist, so we haven't been able to experiment with other techniques for using the Sherpak.

At this point, I would recommend carefully checking whether the Sherpak can be properly positioned on your car, and for the way you would like to carry your kayak. It may be that in our case, we can only load one boat on the roof rack using the Sherpak.

One more point, the surface to which you attach the suction cups, must be really clean; even a little dust will prevent them from getting a good grip. Be sure to carry glass cleaner or denatured alcohol and clean cloths in your car.

The Sherpak seems to be designed well and made of good materials, but it is not a "universal" solution to loading a boat on a car.