The created constraint, if any or false if the constraint failed to set
Example
Adds a console command that makes whatever prop the player is looking at to be kept upright.
concommand.Add( "keep_upright",function( ply, cmd, args )
local tr =ply:GetEyeTrace()
local ent = tr.Entity
if ( !IsValid( ent ) ) thenreturnendconstraint.Keepupright( ent, ent:GetAngles(), tr.PhysicsBone, 999999 )
end )