Historical Rules · 3 July 2020
Rule 701.41a
Official source text from the 3 July 2020 Rules release
Assemble is a keyword action in the Unstable set that puts Contraptions onto the battlefield. Outside of silver-bordered cards, only one card (Steamflogger Boss) refers to assembling a Contraption. Cards and mechanics from the Unstable set aren’t included in these rules. See the Unstable FAQ for more information.