Board Thread:Speculation House/@comment-66.87.78.150-20151129211046/@comment-25857155-20151129213924

I dunno that it was strongly alluded that she can, since she clearly cannot, yet. More than likely the giant knight is her fateher's summon, meaning that she may eventually be able to summon it - but that bears the question of whether it was an actual thing before it became a summon, or if it is a hand-me-down kind of thing through generations.

Yes, Weiss managed to summon a teeny tiny sword, but I don't think that is necessarily a direct relation to the knight. After all, swords are hardly uncommon.