A grouping method for forming a line of products on a packing machine; the grouping method comprising the steps of: feeding a succession of spaced products on a first feed conveyor along a straight, horizontal grouping path at a constant first speed; moving a first compacting member of a first compacting conveyor along the grouping path, downstream from the first feed conveyor and ahead of a first product in the line, at a second speed slower than the first speed, so as to slow down the first product and compact the intermediate products in the line against the first product; moving a second compacting member of a second compacting conveyor along the grouping path, downstream from the first feed conveyor and behind a last product in the line, at a third speed higher than the first speed, so as to compact the last product against the intermediate products in the line; and feeding along the grouping path, directly downstream from the first feed conveyor, a second feed conveyor which receives the products directly from the first feed conveyor, and feeds the products continuously along the grouping path at the same constant first speed as the first feed conveyor; wherein the second feed conveyor is located beneath the grouping path; and said first and second compacting conveyor are located over the grouping path, facing and opposite the second feed conveyor, to form a channel along which said products travel; the grouping method being characterized in that: the starting point of the second feed conveyor is arranged along the grouping path downstream from the starting points of the first compacting conveyor and of the second compacting conveyor; the second feed conveyor extends along the grouping path beyond the first compacting conveyor and the second compacting conveyor; the second feed conveyor engages said products simultaneously with both of said compacting members (23, 25); and the second feed conveyor has a number of pockets, each larger than the line of products in the direction of said grouping path. feeding a succession of spaced products on a first feed conveyor along a straight, horizontal grouping path at a constant first speed; moving a first compacting member of a first compacting conveyor along the grouping path, downstream from the first feed conveyor and ahead of a first product in the line, at a second speed slower than the first speed, so as to slow down the first product and compact the intermediate products in the line against the first product; moving a second compacting member of a second compacting conveyor along the grouping path, downstream from the first feed conveyor and behind a last product in the line, at a third speed higher than the first speed, so as to compact the last product against the intermediate products in the line; and feeding along the grouping path, directly downstream from the first feed conveyor, a second feed conveyor which receives the products directly from the first feed conveyor, and feeds the products continuously along the grouping path at the same constant first speed as the first feed conveyor; wherein the second feed conveyor is located beneath the grouping path; and said first and second compacting conveyor are located over the grouping path, facing and opposite the second feed conveyor, to form a channel along which said products travel; the grouping method being characterized in that: the starting point of the second feed conveyor is arranged along the grouping path downstream from the starting points of the first compacting conveyor and of the second compacting conveyor; the second feed conveyor extends along the grouping path beyond the first compacting conveyor and the second compacting conveyor; the second feed conveyor engages said products simultaneously with both of said compacting members (23, 25); and the second feed conveyor has a number of pockets, each larger than the line of products in the direction of said grouping path. the starting point of the second feed conveyor is arranged along the grouping path downstream from the starting points of the first compacting conveyor and of the second compacting conveyor; the second feed conveyor extends along the grouping path beyond the first compacting conveyor and the second compacting conveyor; the second feed conveyor engages said products simultaneously with both of said compacting members (23, 25); and the second feed conveyor has a number of pockets, each larger than the line of products in the direction of said grouping path.