Jon sez

Liraz is referring in the last panel to her statements to Hugo on page 137.

Explaining what those pop-out braces would look like required me to take Mark into the dark recesses of my basement and unfold a folding ladder. And to explain the use of gunpowder actuated nail guns for fastening wall sill plates to concrete floors. Not that Liraz's braces use gunpowder to drive those spikes into the floor, but the concept is very similar.