Question

when stacking bags of material that are the same width, how should a worker cross - key the bags?
until the stack reaches 4
in each tier above 7
all the way to the top of the pile
every 10 bags high

Explanation:

Cross - keying bags all the way to the top of the pile helps in maintaining stability of the stack. If cross - keying is not done throughout, the stack may become unstable and topple. Stacking until 4’ or every 10 bags high does not ensure continuous stability. And cross - keying only above 7’ is also not sufficient as the lower part of the stack (below 7’) can still be unstable.

Answer:

all the way to the top of the pile