Chairs of not-for-profit organisations are sometimes described as "primus inter pares" - first among equals - in relation to others on the board. However, the reality is that the trustees often look to their chair to make a range of decisions on their behalf and to ensure that the membership of the board is productive.
One of the most demanding tasks for a chair to undertake is dealing with trustees who are underperforming but are not necessarily destructive.
From my experience of working with boards, the recurring characteristics of these trustees include failing to deliver on time, not volunteering themselves or contributing to discussions, or - conversely - talking too much and irrelevantly.
How best to handle such a situation exercises many chairs, and there is no single solution. But I quote one good response I have read: "I arrange to have a conversation with the trustee and say that he or she needs to do better or resign. And they do."
The style might not suit all chairs, but it does at least demonstrate clear ownership of the governance leadership role in the best interests of the board and of the organisation as a whole.