Hostile architecture is an urban-design strategy that uses elements of the built environment to purposefully guide behavior. It often targets people who use or rely on public space more than others, such as youth, poor people, and homeless people, by restricting the physical behaviours they can engage in.

A bird control spike, also known as an anti-roosting spike, pigeon spike, or roost modification, is a device consisting of long, needle-like rods used for bird control. Bird control spikes can be attached to building ledges, street lighting, and commercial signage to prevent wild or feral birds from perching or roosting. Birds can produce large quantities of unsightly and unhygienic feces, and some birds have very loud calls that can be inconvenient for nearby residents, especially at night. As a result, bird control spikes are used to deter these birds without causing them harm or killing them. In an unexpected adaptation, some birds have collected the spikes and used them in their nests.