Definition of obstacles (FEI)

Straight obstacle
An obstacle whatever its construction can only be called straight when all the parts of which it is composed are positioned in the same vertical plane on the take off side, without any rail (pole) hedge, bank or ditch in front off it. A wall with an inclined face may not be called a straight obstacle except in puissance and power and skill competions.

Spread obstacle
A spread obstacle is an obstacle which is built in such manner that it requires an effort both in spread and in height

Here are different examples of obstacle types in profile