Why the boundary has to be written before it is needed
In the moment, a cleaner faces a bad choice: leave a hazard in a public washroom, or handle something they are not equipped for. Both are poor outcomes and both arise from the same omission, which is that nobody decided in advance. Written boundaries convert an individual judgement under pressure into following a procedure, which is the entire point of having one.
The boundary also protects the client. A cleaner injured handling a discarded sharp in your building is a serious event with consequences well beyond the cleaning arrangement. A site that can show it defined the response, provided the means to isolate a hazard and named a contact has a materially different position from one that relied on a cleaner's initiative at midnight.
