Moom and Better Touch Tool
1 Snap to edges
In Moom’s preferences, select Mouse. Click ‘Snap to Edges and Corners’ and fill the checkbox. Open a Finder window and drag it to the left screen edge to fill that half of the screen. Try it with other edges and corners.
2 Use the grid
In Moom’s preferences, select Mouse > Zoom Button Controls. Click ‘Enable Move & Zoom grid’. Hover over a Finder window’s green button to see a grid. Drag a 4-by-2 rectangle on it and your window will resize.
3 Create an action
In Better Touch Tool, select Trackpads. Click Add New Gesture at the bottom of the window, and set it to Five Finger Swipe Left. Under Predefined Action, pick Maximise Window Left. Now try it on a Finder window.