If you have a sidecheck bridle and want to use a separate check bit with it you have to have extra straps added to your bridle. A side check bridle must have straps to keep the bit in place--on mine (big horse bridle) the straps were just 2 separate straps, one each side, sewn onto the crown of the bridle, it wasn't a separate headstall strap like an English double bridle would have for the bridoon bit.
With an overcheck bridle, the overcheck bit is not actually attached to the bridle, it is kept in place with the overcheck strap itself.
If you have a sidecheck bridle and want to use a separate check bit with it you have to have extra straps added to your bridle. A side check bridle must have straps to keep the bit in place--on mine (big horse bridle) the straps were just 2 separate straps, one each side, sewn onto the crown of the bridle, it wasn't a separate headstall strap like an English double bridle would have for the bridoon bit.
With an overcheck bridle, the overcheck bit is not actually attached to the bridle, it is kept in place with the overcheck strap itself.