deep drawn , deep drawn and stretched , or extruded cylindrical aluminium containers are varnished internally and externally , provided with a twostage neck by drawing in and onto the neck is rolled a thread , followed by cutting to length . the drawing - in of the neck , thread rolling and cutting to size are performed with the same container setting . to improve the flexibility , adhesiveness and sliding characteristics , the varnish used is mixed with catalysts , plasticizers and / or lubricants . when the thread is rolled , the container neck is supported from the inside with a quasi - stationary screw - pitch gauge , while from the outside a thread roll is rolled over the neck surface and presses the thread inwards into the neck . the screw - pitch gauge and the thread roll are forcibly guided in such a way that a slip occurs between them and the neck material . as a result the varnish also remains intact in the vicinity of the thread .