Yesterday, the national nonprofit Architecture Lobby announced plans for a national day of action to oppose the Trump administration’s mandate to build a wall on the border of Mexico. On March 10, the lobby has asked that architects and engineers demonstrate against the border wall and the recent immigration policies with a walkout.

From Architecture Lobby:

We are calling for a 45-minute united action on March 10, 4 p.m. EST, for architects and engineers to leave their desks and walk out to demonstrate our power to withhold our individual agency. The goal of this Day of Action is to encourage a grassroots resistance to the border wall from and within architecture and engineering companies across the country . . .

The day of protest coincides with the due date for vendors bidding on construction of the border wall to submit prototypes to the Department of Homeland Security, according to a pre-solicitation notice DHS released last week. As Kriston Capps at CityLab reports, nearly 200 construction and engineering firms expressed interest in working on the project just days after the notice was issued, and a full week before the official solicitation will be posted on March 6. The eagerness of part of the industry to be involved with the construction of the wall contrasts starkly with the refusal of others–and mirrors a broader political divide across the nation.

The 200 interested companies is a remarkable showing, given how condensed the timeline is for submitting full proposals on a massive building project, but perhaps not surprising: For any architecture, engineering, or construction firm, a federal contract of this size would significantly boost business. According to estimates in an early DHS report, building the 2,000-mile-long wall could take over three and a half years and cost $21.6 billion. Some of the companies that have expressed interest in bidding have worked with the government on infrastructure and defense projects before. Caddell Construction, for example, has taken on several projects with the U.S. Army Corps of Engineers and the Federal Bureau of Prisons alike. The defense and engineering giant Raytheon was awarded a contract in 2015 to secure Jordan’s border with Syria.

But many architects and engineers oppose construction of the wall on principle, and Architecture Lobby is calling on them to express their resistance. Some will be the same architects who have been diligently rallying against the American Institute of Architects, architecture’s U.S. professional organization, for expressing support of the Trump administration. They view the wall as a violation of their ethics to promote equitable, safe, and healthy environments for all.

Others have already been expressing opposition in their own way:

The differences in response show a deep divide between the ideologies of prominent coastal architects and the practices of companies that take on federal infrastructure work regularly. It’s a circumstance that could be seen to reflect the broader divided interests of the country, too—between identity politics and economic concerns, coastal elites and the working class.