[There may be a few familiar symbols - runes, perhaps, or even alchemical symbols - but nothing overt.

He perks up at that, nodding.]

Indeed! It seems you've quite the fine control, then.

[He'll let her look at it a bit before he clears his throat.]

Now, you would have to draw this symbol on the floor - in whatever you wish. It doesn't particularly matter what it is, after all. Next, you would place a Catalyst in the center to be used as a 'calling card' of sorts - while you could merely summon without it and hope you are granted what you wish, most often than not your summon will be a Servant that matches you in personality.

[...So, Like, she'd still have a good shot at summoning him regardless, but.]

Having a Catalyst connected to the Servant themselves is a guaranteed way to assure they hear your call.