Telltales ( "tins", "sounding boards", "playboards") are required to be designed in such a manner as to make a distinctive noise when struck by the ball. In addition, telltales must be resistant to impact damage and should idealy have a surface that can be cleaned and allows the attachment of banners, signs, etc. that can be removed without damaging the telltale:

McWil telltales are fabricated using aluminum profiles and are height- adjustable so as to meet all the above-noted requirements and be adaptable
for both professional and amateur play. McWIL – BOSS SENSOR Telltales - signal giving 2 inch sensor line on top of telltale gives optical and sound warning that ball was hit out-of-bounds.

Squash court gamelines (out-of-bounds lines) should provide both a visual and physical indication when a ball strikes immediately above the play wall surface.

McWil owns the mold for the extruded plastic gameline that is used on all squash courts; the gameline is a vivid red and is a concave design that deflects a ball in such a manner as to make the out-of-court landing clear to players and referees alike.