I bought chains from lowes. I also bought some chain hooks. I do it a little differently then most. I take the chain and wrap it around the bar sleeze then put the hook on then let the rest hang off. I do the same with the squat.
The point of using chains is to add more resistance to mostly the top of the lift and to prevent the bar from jumping off your back when you do dynamic effort squats.
I can not say if it has helped my lockout yet but I am pretty sure it will.
Also, I bought mini, light, and average bands from elitefts.com awhile back. The good thing about buying bands from them is they send you a book on how to use and setup the bands. If you have a power rack it is easy to set those up for squats and benching. Deadlifting is tricky though and you either need a platform or db's. The bands worked great for benching lockout. I recommend them for box squats too because they force you to stay really tight in the core.
Discipline makes you mentally and physically tough!
Currently making everything stronger!!
Once I stick to the program I am going to get really strong.