Ford ranger and tonno covers security?

I'm going to buy my first truck tomorrow, 2008 ford ranger. I notice that there's no lock on the tail gate. So my question if I bought a tonno how does it lock? What will I need? Some help please. Also I'm looking to buy a cheap tonno like the tri fold ones, will I have to install a lock on the rain gate? But how does that lock the tonno? Very confused

Look for the models with the big lips.
the cover locks down at the corner and the lip hangs over the back so the gate is blocked