In order to be used for sustained fire it was important to be able to fix the gun down, thus providing a stable platform. As with many similar machine guns of the period, the German Army opted for a conversion kit which was both simple and compact.
Contained in the bag as shown, it comprised several parts, which when assembled, allowed for the MG13 to be deployed in this fashion.
There are four steel pins which could be driven into soft ground in order to anchor the gun on a sustained-fire platform.
The next item is designed to attach to the tubular stock of the MG13 and support the rear of the gun. This in turn slotted into the part shown at the bottom of the photo.
The next part is a mount for the bipod to sit in which, due to the required span, was hinged in the middle in order to assist in transport. The ends of this each have a square hole to accept the pins. There are also leather straps which further aid in holding down the gun when in use.
The final part is the mounting for the rear of the gun which has a marked scale of degrees for accurate targeting. Additionally, there are adjustable locking nuts to both prevent the gun from falling out of the apparatus and to restrict the overall arc of fire, if desired.