How to model a Lego piece in Blender 2.77
Step 9: Move the selected faces along the z-axis.
Step 10: Enter Delete/Del » Faces to delete the selected faces
Step 11: Switch to the Object Mode » Enter Z to switch to Solid Viewport » Move the rest of the sphere to the top of the cube.
Step 12: Press Numpad 7 to view from the top of the scene
Step 13: Press S to scale the rest of the sphere » Move it to the position as the image below
Step 14: Hit Shift + D to duplicate 3 objects from the rest of the sphere » Press G to move it. Then select all four spheres, press Ctrl + J to join them to one which named as “Sphere.00x”.
Step 15: Enter Numpad 1 to view the front of the scene » Press G to move these spheres to the surface are of the cube
Step 16: Right click on the cube » In the Modifiers, click on the Add Modifiers list » Select Boolean Modifier