eba6f2a0_de___BlackBerry_Composer___6_0__Description
[Element] limits [Description] 
The limits are lines that show the edges of the canvas. You can use the limits to resize the canvas by dragging them to the appropriate size. You can show or hide the limits, or lock them to prevent you from accidentally moving them.
Project window and workspace - User Guide - BlackBerry Composer - 6.0