What I am referring to is construction regulation 26.1(2)
(2) Despite subsection (1), if it is not practicable to install a guardrail system as that subsection requires, a worker shall be adequately protected by the highest ranked method that is practicable from the following ranking of fall protection methods:
Practicable is the word that allot of people are a mis-interpreting for practical.
Practical means; sensible, useful, easiest for the situation,
Practicable simply means 'that is possible'
Therefore in the regulations we cannot simply choose the easiest or most practical method on the list, we must choose the highest ranked method that is possible regardless of difficulty, if guardrails can be installed, they must be installed.