Originally Posted by
bergerud
Construction lines cannot be snapped to. They are just an inert guide. Unselected geometric objects like circles and lines also appear like the dotted construction lines. They can all be toggled on and off.
The grid is also just an inert guide unless the snap to grid is toggled on. When the snap to grid is on, an object's control points (yellow and red dots) will jump to the grid as you move the object around. This is extremely useful for laying out objects and parts of objects in exact positions relative to each other. I almost always draw with the snap grid and snap to grid on.
The default size of the snap grid is 1/2". It can be changed to most any size you want. I usually jump between 1/4", 1/8", and 1/16". Use exact fractions if the decimal gets rounded after three places. For example, 1/16" and 0.063" are not the same. (Be aware that any time you OK the snap grid dialog, the round off, if displayed, will be applied. You have to retype 1/16".)
A very useful use of the snap grid is to snap control points of objects to control points of other objects. This can be done even if the control points end up off of the grid. For example, suppose one has hexagon and one wishes to place drill holes on each vertex of the hexagon. Place the drill holes on the snap grid. Move the hexagon to snap a corner on a drill hole (the same snap position). Now with the hexagon and the drill hole selected move another corner of the hexagon to another drill hole. The first drill hole, as it is also selected, will follow and stay attached as you do this. Repeat the procedure for all the drill holes and you will have your drill holes exactly placed around a hexagon even though the corners of the hexagon do not all fit on the grid.