Seems to be pretty secure, I use this to secure the bed in the city. I love that I don't need to use they key, and can just use the tailgate lock, and release pull cord. The last thing I need is to carry another key. Fit and finish are top notch. Install is not bad, took about 2-3 hours, if I did another I could install it in 45 minutes. It calls for three drain holes to be drilled in the bed, not sure yet if I am going to do this or not.
2016 Toyota Tundra Install
Overall I am very pleased with this tonneau cover. The installation takes a bit longer on the Tundra since the bed rail system must be lowered. After that, the remaining install is straight forward. I have not installed the drain hoses yet, there's just something uncomfortable about drilling into the side of a new truck, but I will have to come up with a solution soon. The cover rattles slightly on rough roads but otherwise, it has been perfect.