Method for forming a holder (1), by blow moulding, with a wall (3), whereby a preform is pushed against a first and second mould part (10, 11) to form an intermediate form, in which the second mould part (11) is moved and takes the intermediate form with it in order to form an edge (5) between the first and second mould part (10, 11), whereby the mould parts (10, 11) are such that the edge (5) includes a first and second edge part (13, 14)), of which the second (14) is closer to the wall (3) than the first, of which the first (13) makes an angle (α) to the direction of movement of the second mould part (11) and of which the second (14) makes a larger angle (β) to it.