Isometric grid
To create an isometric grid, select the isometric grid tool. To numerically create the rectangle, click once on the document.
To draw a front face grid, click and drag to the opposite edge.
To create a side grid, hold down the command/control key after you begin dragging. To create a top or bottom grid, hold down the alt/option key after you begin dragging. The cube icon in the CADisometric palette indicates which face you are drawing. Hold down the shift key to create a grid square in isometric view.