What action is considered an illegal placement related to signage?

The action considered an illegal placement related to signage in this context is the illegal placement of a sticker. Stickers are often placed without the necessary permissions from property owners or local authorities, which can lead to violations of local signage regulations. These regulations are in place to maintain public order, aesthetics, and safety, and unauthorized stickers can detract from the appearance of public spaces or obscure important information.

The other options involve actions that typically follow different regulatory processes. For instance, the placement of promotional advertisements on public property often requires specific permits or adherence to local ordinances governing advertising in public spaces. Posting flyers on designated boards is generally permissible if those boards are meant for public announcements and usage, adhering to the intended guidelines. Fixing a sign without a permit is also an illegal act, but it primarily pertains to larger signage constructions, which may face different legal requirements compared to the unauthorized application of small stickers.

In summary, the illegal placement of a sticker is distinctly recognized as unauthorized and generally disregards any regulatory framework designed to manage visual clutter and ensure compliance with local laws.