Seven of Manhattan’s elite law firms took the rare step of signing on to a single letter to the Securities and Exchange Commission to voice their opinion on how the agency should implement a proposal to allow shareholders to nominate company directors.

Lawyers involved in drafting the letter, submitted Monday, acknowledge it was rare for one letter to come from all the firms, which included Cravath, Swaine & Moore, Sullivan & Cromwell and Wachtell, Lipton, Rosen & Katz.