The Portable Sawmill supports a maximum of 2.5 units width of logs (though it can process logs slightly bigger than that by using glitches to push the log inside of it, or up to 3 units in width if the player chops them into smaller chunks and inserts these chunks sideways into the sawmill) and cannot support logs with more than 11 units of length.
When a player buys the Portable Sawmill, you can carry it around in your vehicle and place it down whenever you want to mill any logs. The Portable Sawmill, when opened, will become green and transparent (just like any other blueprint) and you can place it anywhere where trees can grow (except the Lone Cave) and your land.
When placed, you can place in logs like any other Sawmill to turn them into planks to sell at the Wood Dropoff. Lastly, to put the Portable Sawmill in it's boxed form so you can carry it elsewhere, you simply need to press 'E'. If a player was to go far away from their Portable Sawmill, it will be repackaged in a box at the owner's base.
The Portable Sawmill is very similar to the Sawmax 02, the only notable differences is that is has a small Funnel Conveyor at the output of the the sawmill and also the Plank Cross Section is removed with the max size sign placed in the middle.