Joele Frank, Wilkinson Brimmer Katcher supports Germany’s Knauf in its proxy fight with building products competitor USG Corp. of Chicago.

Knauf, which has made a $5.9B bid for USG, is urging shareholders to vote against four USG director nominees at the May 9 annual meeting.

USG, which relies on Sard Verbinnen & Co., said Knauf’s bid is “wholly inadequate, opportunistic and does not reflect the intrinsic value of the company.”

Knauf, which owns about 10 percent of USG, knocks it for failing to engage in serious negotiations or show “substantive evidence to support its claim that the company is worth more than $42 per-share.”

The Germans have a key ally in their fight. Warren Buffett’s Berkshire Hathaway, owner of 31 percent of USG, plans to vote against the four directors up for election.

Joele Frank, Ed Trissel and Annabelle Rinehart represent Knauf. SV&C’s Jim Barron and Pam Greene work the media for USG.