A device for trimming around stationary objects is disclosed as a rotary mowing attachment with a cutting head assembly slidably coupled to a carrier assembly that is positioned by a slope control circuit and controller. The cutting head assembly has at least two counter-rotating blades, at least one rotator motor configured to rotate the cutting head assembly about a cutting head central axis, at least one blade drive motor configured to drive the at least two counter-rotating blades, and at least one lateral motion drive motor configured to move the cutting head assembly position relative to the carrier assembly.