There's two ways you can inflict force on something.
You can do it via kinetic energy (punching, running into it), which requires speed to be built up first.
You can also do it via pure muscle (pushing, pulling, lifting), which requires no speed build up.
Striking Strength measures the first thing: how much energy you can exert if you can do whatever you want to achieve it.
Lifting Strength measures what your muscles can do on their own without any speeding up beforehand.
Lifting something off the ground is the most obvious example of this, but technically other things can be used to calculate it.
I'm not sure what you mean exactly by blocking, but:
If an object is flying at you, and you completely stop it just by tensing one of your muscles (not by punching it back) then presumably this could be extrapolated to Lifting Strength as well.
If you want the specifics on that, you should ask the calc group.