There are three primary methods to control the size of the front triangle. Each method allows control of two distinct dimensions. Notice that if you choose to control the front center distance, then you will also have control of the head tube length. If you choose to control effective top tube length, then you will also have control of the top tube angle. If you choose to control the horizontal position of the handlebar relative to the bottom bracket, then you will also have control of the vertical position of the handlebar relative to the bottom bracket.

Be aware that when you select a pair of dimensions from this list, not only are these the dimensions that will be used to drive the geometry, they are also the dimensions that will remain fixed as you change other dimensions on the bike. The other two pairs of dimensions will then be vulnerable to being changed as a result of other dimensional modifications. For example, if you choose Handlebar from BB (X and Y) to set the handlebar position, you can later go and change the stem length and the handlebar will remain fixed. The frame will adjust to accommodate the change in the stem. This may cause the head tube length, front center, effective top tube length and top tube angle to change as a result.