For an overview on creating, visualizing, and simulating mover constraints, including AlignPosition, see Mover Constraints. Also see Roblox Units to understand how Roblox units compare to metric units.
An AlignPosition constraint applies force to move two attachments together, or to move one attachment to a goal position. As indicated by the name, it only affects the position of the attachments, not their orientation (to align attachments by orientation, see AlignOrientation).
By default, the constraint only applies force to Attachment0, although this behavior can be controlled through ReactionForceEnabled.
Force Location
By default, force is applied to the parent of Attachment0 at that attachment's location, meaning that if the parent's center of mass is not aligned with the direction of the force, torque will be applied as well as force. Alternatively, force can be applied to the parents' center of mass by toggling on ApplyAtCenterOfMass.
Reactionary Force
By default, the constraint only applies force to Attachment0 while Attachment1 remains unaffected. If desired, force can be applied to both attachments in equal and opposite directions by enabling ReactionForceEnabled.
Force Magnitude
You can configure the AlignPosition constraint to apply the maximum force that constraints allow through the RigidityEnabled property. When true, the physics solver reacts as quickly as possible to complete the alignment. When false, the force is determined by MaxForce, MaxVelocity, and Responsiveness.
Attachment Mode
The Mode property specifies whether the constraint uses one or two attachments in calculating its goal. By default, this is TwoAttachment, meaning that the constraint disregards Position and attempts to move Attachment0 to the position of Attachment1. If set to OneAttachment, the constraint disregards Attachment1 and attempts to move Attachment0 to Position.