The same way Pitsco makes the Tetrix brand of robot parts, ServoCity makes the Actobotics brand of robot parts. Actobotics uses a different hole spacing and pattern in its aluminum channels than Tetrix so it's probably preferable to stay with one system or the other. In order to attract more FTC teams to the Actobotics system, ServoCity offers free parts, a 25% discount, and even sponsors a number of FTC teams for $1000 worth of Actobotics parts. Even if you don't use the Actobotics system, the discount can be used for servos and other robot components so every team should consider signing up for some or all of the offers below.
ServoCity FIRST Hub - sign up for their FTC Newsletter and get free parts
Brainstormers (FTC8644) from Lexington, MA has a couple of videos on using Actobotics: