locking out the knees during SLS progressions?

i recently learned that, during GST, i need to lock out the elbows whenever i straighten the arms.  and i started wondering if it's the same case with the knees.

 

should we lock out the knees whenever possible during the SLS progressions?

Yes lock out the knees.

Yup, fully extended and locked.

how do you mean locked knee? if you can example pls.

Talal,

 

When you fully extend your leg and flex your quads, the knee cap raises. That's locked.

 

 

-Nash