Example:

A project owner appoints an engineer to design the heating and cooling system for a new building which is to be constructed.  A major manufacturer of heating and cooling equipment bribes the engineer to specify its product in the design.  The engineer does so, and persuades the project owner that that supplier’s equipment is superior, and should be purchased.  In consequence, all contractors bidding for the construction of the project are compelled to include the equipment of that supplier in their bids, and that supplier can consequently charge a higher price than it would have done had there been competition from other suppliers. 

Explanation:

This form of corruption can be difficult to prove, as there is often a large degree of subjectivity in design.  The engineer may claim that he genuinely believed that the supplier’s products were the best, and therefore should be used by the project owner.  It consequently may be difficult to disprove this, or to prove corrupt intent, unless the actual bribe can be uncovered and proven, or unless the nominated supplier was obviously and clearly inferior to alternatives.