In this instructable i will be showing you how to make a Lego brick i don't have a 3d printer so it hasn`t been tested but i am almost positive it will work. If you have a 3d printer please consider printing it for me i will leave the file below
http://www.123dapp.com/FullPreview/Index.cfm/ID/1648165

Step 1:

Dimensions of the main brick body Length: 31 mm Width: 15.5 mm Height: 9 mm. Find primitives in the bar menu and select the cube enter in these dimensions 31, 15.5, 9.

Step 2: Placement of Studs

Firstly the studs have a radius of 2.5 mm and are 1.5 mm high. The studs are 1 mm from the sides, front, and back and 3 mm from each other. You may want to use a carpenters square to check that they are lined up perfect.

Step 3: Bottom

First you will need to hollow out the bottom go into modify then shell once in the modify menu. Now a mini bar should have popped up on the bottom of the screen in the box that says thickness inside type 1 then click on the bottom of the square now you should have a hollowed brick. Now grab the cylinder from primitives and set it with a radius of 3 and a height of 9 now place centered in the brick 3 mm from the inside on one end. Now shell it with a inside thickness of 0.5 place two more exactly the same 1 mm from each other shell them too. Now you are done your 123D design Lego brick now you can send it off for 3D printing unfortunately i don't have a 3D printer so could one of you please tell me how it works thanks.

- TREX ZoaR0K

P.S. Sorry for starting a lot of sentences with now