Definition on the line to the blind...

...There is actually an earlier set of boundaries on the slot to the blind on the far land. About halfway to the bird from the far end of water, two equi-distant bushes or shrubbery/trees define goalposts, at least insofar as the line to the blind is concerned. This is not to say that this boundary or the farther one near the end of the blind are mandatory to successful completion of the blind, but they do define the line.