Yes. One of the pilots, usually an F/O, is required to complete a "main deck procedure" prior to departure. It involves checking emergency equipment, checking condition and position of all doors and windows, verifying door control panel switches are configured properly and door locks are secure, verifying all the floor locks in every pallet position are "up", checking position, condition, segregation, and labeling of hazmat, checking condition of cargo nets/restraints, and checking for general condition of the pallets (among other things). That's the way it is where I work anyway, even if there is a dedicated loadmaster on board, we're still required to check it. Obviously I can't speak for National. The 747 has aisles on both sides of the main deck that my fat ass barely fits down (the aisle is maybe a foot wide?), but you walk down those to look at everything. Sometimes if the plane is completely full you can't get to the aisle on the aircraft's right; in that case you check what you can.
At the end of the day, a lot of trust still gets placed in the loadmasters, especially when dealing with outsized cargo or vehicles that can have a lot of complex restraints. I don't build pallets for a living, so I just use my best judgement and the manuals/guidelines I have to determine if everything looks suitable. When in doubt, you go tell the captain and the loadmasters, then make a decision once a potential issue has been brought to everyone's attention..