Like conic projections, cylindrical projections can also have tangent or secant cases. The Mercator projection is one of the most common cylindrical projections, and the equator is usually its line of tangency. Meridians are geometrically projected onto the cylindrical surface, and parallels are mathematically projected. This produces graticular angles of 90 degrees. The cylinder is "cut" along any meridian to produce the final cylindrical projection. The meridians are equally spaced, while the spacing between parallel lines of latitude increases toward the poles. This projection is conformal and displays true direction along straight lines. On a Mercator projection, rhumb lines, lines of constant bearing, are straight lines, but most great circles are not.
For more complex cylindrical projections, the cylinder is rotated, thus changing the tangent or secant lines. Transverse cylindrical projections, such as the Transverse Mercator, use a meridian as the tangential contact or lines parallel to meridians as lines of secancy. The standard lines then run north–south, along which the scale is true. Oblique cylinders are rotated around a great circle line located anywhere between the equator and the meridians. In these more complex projections, most meridians and lines of latitude are no longer straight.
In all cylindrical projections, the line of tangency or lines of secancy have no distortion and thus are equidistant lines. Other geographic properties vary according to the specific projection.