RTFM

Annie rings the doorbell and waits. Nobody answers. She checks that she's at the right door – yes, this is grandpa Karl's apartment. She rings again. A window on in? one of the adjacent houses opens and she hears Isabelle quietly calling her.
Annie, we're over here.
She walks over.
Which door?
Number 15, I'll let you in.

Lucas and Karl are also inside.
Karl says: We needed a little more space. This place has been vacant forever, might as well use it.
Annie slides her shoes off and leans her bag against the wall. Then, they go to the living room where cables and computer parts are all over the floor. Lucas sits in front of the rack between two opened boxes. The rack's side panels had been removed, revealing the rails holding the various devices inside and their power cables. Lucas is pushing a circuit board into a half-assembled device that hangs out the front. Karl goes over to a stool next to the rack, carefully avoiding stepping on things, and sits down.

Annie sits down next to Lucas and watches as he carefully inserts one board after the other. Karl is looking at the manual and tells him to set some tiny switches on the front of some of them.
Karl says: Annie, can you hand me these four gray ribbon cables?
She looks around, lots of different cables everywhere.
The wide, flat ones to your left.
He takes them and plugs them somewhere into the back of the rack.

Isabelle grabs the terminal from a corner of the room and lifts it onto the rack. Meanwhile, Annie and Lucas start collecting the cables and loose parts from the floor. Karl plugs rack and terminal into power and connects a cable between the terminal and one of the devices in the front of the rack.