Expert Role Pair-of-Hands Role Collaborative Role
I have neither the time nor the inclination to deal with this problem.  You're the expret; find out what's wrong and fix it.  You have a free hand to examine the operation and do whatever analysis is necessary.  Keep me posted on our findings and what you intend to do. I have neither the time nor the inclination to deal with this problem.  i have examined the deficiencies and have prepared an outline of what needs to be done.  I want you to get it done as soon as possible.  
The manager elects to play an inactive role. The consultant takes a passive role. The consultant and manager work to become interdependent.
Decisions on how to proceed are made by the consultant, on the basis of his or her expert judgment. Decisions on how to proceed are made by the manager. Decision making is bilateral.
Information needed for problem analysis is gathered by the consultant. The manager selects methods for data collection and analysis. Data collection and analysis are joint efforts.
Technical control rests with the consultant. Control rests with the manager. Control issues become matters for discussion and negotiation.
Collaboration is not required. Collaboration is not really necessary. Collaboration is considered essential.
Two-way communication is limited. Two-way communication is limited. Communication is two-way.
The consultant plans and implements the main events. The manager specifies change procedures for the consultant to implement. Implementation responsibilities are determined by discussion and agreement.
The manager's role is to judge and evaluate after the fact. The manager's role is to judge and evaluate  from a close distance.  
The consultant's goal is to solve the immediate problem. The consultant's goal is to make the system more effective by the application of specialized knowledge. The consultant's goal is to solve problems so they stay solved.
Challenges
in a climate of fear/mistrust, consultant might not get what they want/need.

recommendations carry no sense of ownership for the client.

Inappropriate assessment by manager means implementation will be flawed.

Managers prefering this role for consultants see collaboration as questioning managers authority, experience, or both.

Those preferring expert see this as foot dragging. 

Those who prefer pair-of-hands see this as insubordination.

Source: Peter Block's Flawless Consulting, pp. 21-27,
based on Ed Shein's Process Consulting Revisited: Building the Helping Relationship.
Ashley Guberman, Organizational Development Resources