What type of bracket has two pieces of angle facing in opposite directions and bolted together with slotted holes to allow for adjustment?

The adjustable angle bracket is designed specifically to have two pieces of angle that can face in opposite directions and be bolted together with slotted holes. This configuration allows for flexibility in positioning, as the slotted holes facilitate adjustments to achieve the desired alignment or angle between the pieces. This is particularly useful in applications where specific angle settings may be required or where slight modifications are necessary for proper installation or operation.

In contrast, fixed angle brackets typically do not allow for adjustments; they are designed to hold components in a set position. Rigid brackets are also meant to provide stability without the capability for adjustments. Standard angle brackets usually refer to a basic design that does not include any features for angle adjustment either. Therefore, the feature of slotted holes enabling adjustment clearly identifies the adjustable angle bracket as the correct answer.