The #6 on a standard spacing rule equals a _____ size bed joint.

In masonry, the spacing rule is used to determine the thickness of mortar joints, which are crucial for the integrity and appearance of a masonry wall. The "#6" designation on a standard spacing rule corresponds to a specific bed joint size, measured in inches.

The standard designation for a "#6" bed joint is 3/8". This measurement is commonly used in construction as it provides a good balance of strength and flexibility in the mortar joint, allowing for proper bonding between the masonry units, such as bricks or blocks. A 3/8" joint is widely accepted in industry practices, ensuring consistent thickness, which is important for the overall aesthetics and performance of the masonry work.

This particular joint size facilitates effective drainage and allows slight adjustments during installation, which can be vital for achieving alignment and leveling. It is also important to note that using standard measurements like the #6 ensures compatibility with various construction standards and practices.