A tide cycle you can turn by hand. On a windowsill or kitchen table, spin the tide arm to compare Moon positions side by side with the fixed sun arrow and see which ones stretch the tide range and which ones shrink it. Coastal science teachers, tide-chart hobbyists and Montauk sailors keep it within reach to test a prediction before checking the real chart.

How the tide arm turns. Turn the tide arm by hand around the tan center post that rises through the orange earth hub. The arm carries the purple moon marker to one side of the base, sweeping it past the blue sun arrow fixed near the rim. Line the marker up with the arrow for the widest swing, turn it square to the arrow for the narrowest.

Six pieces, one pivot. Take it apart and six pieces come free: the green phase base anchors the blue sun arrow and holds the tan center post at its middle, the orange earth hub caps that post, and the purple moon marker plugs into the arm's outer end, which spins back onto the post to close the loop.

Fit, finish and scale. Set it down and the base sits low and wide, its center bored for a smooth pivot so the tide arm swings freely without wobble. Two shallow tick marks cut into the front rim flag the alignment and quadrature angles. Every piece keeps a fine layer finish and tight, precise seams where the hub caps the post and the marker seats on the arm.