I made one in about an hour and a half out of some 3/4 in copper pipe, a piece of 1/2 in plywood and a piece of scrap carpet. It is built for a mod v hull boat and once a dog uses it a couple times he has it down pat. All you have to know is where the water level is going to be and solder it together. I had all this junk laying in my barn but if you had to buy it even at the high prices now you could make it a lot cheaper than you can buy them.