My recent posting on You Tube shows a classic method for achieving straightness. ( David Charlesworth woodwork channel ).

I have found that thin acrylic from the sign shops makes very superior reflectors.

The far stick has a protruding inlay of ebony so that the white keys do not get lost in a white wall.

This is 1/16" thick and sticks up no more than 5mm. It is easily replaceable if the sticks needed truing in the future.

David Charlesworth