The Tankgewehr 1918 (AT rifle) was encountered more often. Produced from May 1918 to the end of the war (by which time the factory was producing about 300 per day). Total production was about 16,000 by the Armistice.
https://tanks-encyclopedia.com/ww1/Germany/AT-guns/mauser-tankgewehr-m1918/The guns were issued at a rate of 2 or 3 per Regiment and the first ones were assigned to the areas most likely to face tanks (thanks to reconnaissance or intelligence). A special anti-tank group was created and attached to the Regimental HQ. Each gun would be crewed by two men, the gunner and the loader/spotter. Together, they would typically carry 132 rounds split between three 20 round leather bags and a 72 round box. These men were chosen for their bravery as well as their stature, to allow for more effective use of the weapon. When a tank attack was in progress, the 2 or 3 guns would then be sent to the main line of resistance and wait until the tank was within 300 metres or so to engage.
The Tankgewehr was not a one-shot kill weapon but was meant to be used in conjunction with other Tankgewehrs, as well as machine guns and riflemen using K-bullets. The Tankgewehr operators were taught to fire at the areas of the tank that contained either crew members or vital equipment like the fuel tank or engine. The German General Staff published a 3 page illustrated leaflet based upon several tests they conducted titled, “Merkblatt für Tankbekämpfung : (Kleiner englischer Tank)”. In it, it advised that the Tankgewehr guns fire at the machine gunners, drivers or fuel tank placements in order to render the tank inoperable and defenseless to grenade-wielding anti-tank teams.
However, the Tankgewehr didn’t need to penetrate in order to achieve its goal. Tanks of 1918 were built from riveted armored plates and hitting them with enough force could cause buckling, rivets to pop, as well as spalling. These things could cause damage to components and crew members alike and force the tank to stop or at least slow down, making it easier to be targeted by more powerful weapons.