Grid Overlay -
Pressing Shift-G while looking at a square foundation will attach a Grid Overlay, a large 41x41 red grid.

Each square represents the size of one foundation. The Grid Overlay can provide a quick way to see just how flat your new building spot actually is, and give you an idea of how big the area is in foundations. It's main use is to facilitate Snap-to-Grid.

Snap-to-Grid -
Pressing Ctrl-G while a Grid Overlay is deployed will toggle Snap-To-Grid.

While within the bounds of the grid, any square foundation you equip to place will "snap" to the grid, aligning itself both horizontally and vertically. It can also align Large/Medium/Tek Crop Plots horizontally. The structures still follow normal building rules. They do not actually snap to the grid, as the grid is not a structure and will provide no support.
STG can help line up separate structures across distances, build more easily on uneven terrain, or perfectly line up crop plots from any mod onto any square foundation. Other structures may be allowed to snap to the grid at a later date.

Notes -
- Shift-G and Ctrl-G will not work while placing S+ Crop Plots due to their use of G to toggle their own snapping logic. You can either cancel placement temporarily to toggle the Grid Overlay and STG, or you can rebind Drag to a different key, since technically I use Shift-Drag and Ctrl-Drag.
- Snap-to-Grid works best with vanilla structures if No Collision is enabled in the ini settings. S+, SS, CKF mods all have No Collision built-in so you should not have to worry about this setting if you never build with vanilla parts.
- Grids cannot be attached to structures that are on moving platforms (platform saddles, rafts, skiffs, etc).
- Snap-to-Grid will not work if the currently placing structure is too close to a dino, structure, raft, skiff, etc).
- Grids are client-side. They will only be visible to the player that creates them.
- Due to the unusual size of CKF Legacy foundations, the grid will not align perfectly with them over distances. An imperfect solution to this would require adding a completely different grid with different dimensions, but I don't plan on doing that any time soon, if ever.

This is the first release of the Snap-to-Grid system. There will further improvements in the future.