Board interlock

A board interlock is identified when the same named individual appears as a Section 16 filer, a director or officer, on Form 4 filings at two separate companies. The tab builds this by matching filer identities across the full universe of Form 4 filings rather than pulling from any company's own published board roster, which means the interlock is discovered entirely through trading activity, not through governance disclosures like proxy statements.

Read a board interlock as evidence of a real, documented person sitting on both companies' boards or in both companies' executive ranks, useful context when the same insider's trading pattern at one company might inform how to read a smaller or less-followed trade at the other. Because interlocks are built from actual filers, not job titles pulled from a bio page, every interlock the tab shows is backed by a specific, dated Form 4 at each company, not an inference.

This is a genuine coverage gap, not a minor caveat: the interlock detection only catches a director or officer who actually filed a reportable Form 4 transaction, generally a purchase or sale of roughly $100,000 or more, at both companies. A director who sits on both boards but never traded stock at one of them, whether because they simply held their existing grant without buying or selling, or their holdings never crossed the reporting threshold, will not show up as an interlock even though the real-world board overlap exists. That means the interlock count is a lower bound, not a census of actual shared directors; the true number of overlapping board members between any two companies is very likely higher than what the tab surfaces.

An individual files a Form 4 as a director at Company A showing an open-market stock purchase, and separately files a Form 4 as an officer at Company B showing an option exercise. Matching those two filings by the same named person surfaces one board interlock between Company A and Company B. A different individual sits on the board of Company C and Company D but has held the same modest initial grant at Company D without ever buying or selling since joining, so no reportable Form 4 exists there. That real interlock between C and D never appears on the tab, since the underlying trigger, a filed transaction, never happened at Company D.