There are alignment arrows and alignment lines molded into the new bayonet connector, but in a dimly lit room, it's impossible to see them at a normal reading distance.
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There needs to be some light and you have to look closely.
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In this case, you align Arrow 1 with the line and push forward until both pieces are fully engaged, then you twist the connection about 1/4 turn (similar to Plug-it cord) until Arrow 2 is in alignment with the line.
In theory, it's a simple practice but I struggle with it every time whether it's with the 27mm or 36 mm hose. Also, it's easier to remove the fitting from the saw, install the hose and then reinstall the fitting on the saw.
Festool really should consider over-molding the arrows & lines on the bayonet connector in a contrasting color to make them more visible.