Using Ortho Mode and PolarSnap

Commands

ORTHO Constrains cursor movement
POLAR Constrains cursor input to specified angles and radial distances

System Variables

ORTHOMODE Constrains cursor movement to the perpendicular
POLARANG Sets PolarSnap angle relative to the current UCS
POLARDIST Sets the distance from the last point for PolarSnap intervals
POLARMODE Controls whether PolarSnap is constrained for distance and angle
POLARSTYLE Controls whether PolarSnap coordinates are displayed in tooltips