I use an Undercover brand tonneau cover. It has an integral lock, and only weighs 50# so I can take it off and put it on by myself.
Craig and Carol
1997 34' Excella 1000
1970 27' Overlander, International
2009 Ford F150 5.4L
ProPride hitch with 1400# bars
Past President Southeastern Camping Unit (12)