In this video, I will demonstrate how you can slide the saddle fore and aft along the rails in BikeCAD using the Fore and aft slider. As you can see, if we've assigned a saddle height of 700mm, BikeCAD will retain this saddle height no matter where we position the saddle along the rails. It maintains this saddle height by sliding the seatpost in and out of the seat tube. As the saddle is slid further forward, although the distance from the bottom bracket to the top of the saddle will remain the same, the saddle will be positioned closer to vertically over the bottom bracket. This change in position makes the saddle slightly higher off the ground increasing the overall height of the bike. Because BikeCAD scales the view according to this height, you'll notice the scale of the display changing as you move the saddle. If you'd like to lock the scale of the display you can do so with the Lock scale icon.
The slider corresponds to the position of the saddle clamp along the straight length of saddle rail. The length of this straight section is controlled by dimension R in the Saddle dialog box. In BikeCAD version 10.5 we can control the clamp position with greater precision through the new dimensional input field. This input field specifies the distance in millimetres by which the saddle is shifted forward or backward from the centre of the rails. If we should ever change the length of the straight section of rail, the distance from the centre of the saddle clamp to the centre of the rails will remain the same. However, the slider will shift slightly to reflect how that clamp position now represents a different percentage of the overall length of rail.