The "Welcome Mat V1 (Legacy)" is available under "Other Gadgets" in the "CV1 (Legacy)" tab of the Palette and - after activating the search field - in the "Gadgets" tab of the Palette . You tap it and pull the trigger on the Maker Pen to place it somewhere in a Custom Room. Visitors to this custom room will then spawn above the welcome mat. You can edit a welcome mat with the "Configure" mode of the Maker Pen and specify a room name for it; in this case, the welcome mat only works when visitors are coming from that specific room.