Grid manipulation refers to the manipulation of the size and/or shape of a grid. This has previously been believed to be an exploit but is not considered one by CCP. This is therefore a valid tactic in EVE Online. To investigate this further we should first look at what a grid is.
A grid is the space surrounding any object in space. This is typically a sphere approximately 250 km in each direction starting from the object the grid is surrounding. In other words if your ship is alone deep in space with nothing surrounding your ship, there will be an invisible sphere surrounding your ship, 250 km in every direction. Anything within this sphere will be visible in your overview. An object located just outside of your grid will not be visible in your overview.
Grid wallsAll grids have an invisible wall surrounding them that your ship can pass through, into the next grid. These walls can be moved and thus the grid is manipulated.
As stated earlier grid manipulation is the moving and manipulation of grid walls. This move can be inwards in the grid, decreasing the size of the grid or outwards, expanding the size of the grid. There are several ways of accomplishing this but they all include moving or placing an object (any object) very close to the boundary of the original grid and thereby extending the grid outwards from the new object. The easiest way is to fly in a straight line from an object in space for less than 250 km. There you have to either drop some sort of placeholder, like a jet can or any other object and then continue to fly in the same direction. Or have another ship continue on the same path onward using the former ship as a placeholder. After doing this the grid(using these 3 objects in space) can be a total of 1000 km in length (500 km(the original diameter)+250 km(the first object extending the grid)+250 km(the second object)) however this is only extending the grid in one direction. The width of the grid is therefore only 250 km still.
All objects in this 1000 km long grid will appear on the same overview at this point. There are then several different manipulations one can do like removing the placeholder in the middle or extending the grid in a new direction creating an L shaped grid or indeed any possible shape with patience and skill. Such manipulation can create space in between 2 pockets of the same grid where another grid is present. This whole process is quite complex but not an exploit of game mechanics.