This easy to build canoe and kayak rack is simple to build and use, though it does take up a little more space than some of the other designs I've posted here. It's pretty easy to build:
1. Dig 4 post holes. Each pair to which you will bolt a cross member should be as wide apart as you want the rack to be (3 feet times the number of canoes you have). Put the pairs about 9 or 10 feet apart. That's half to two-thirds the length of most canoes and kayaks and supports well enough so that summer heat doesn't cause the boats to sag and distort the hulls. Use treated posts. They should stick up about 2 to 3 feet depending on your comfort level and be treated. Pour concrete around them to set the posts.
2. Lag bolt a 2x12 pressure treated cross member to the posts as shown in the picture. Pad the cross member to protect the boat. I like to buy used fire hose from local volunteer fire departments and screw it on top of the cross members n accordion pleats. The pleats keep the canoes from sliding around on the rack.
4. To make tie-down easier, screw some eyelets to the face of the cross members to create attachment points for bungee cords. Tying down the canoes prevents them from taking flight in a wind storm.