headbox 21 across the width direction 58 of the fourdrinier 37 for which the jet 23 emerges direction 58 is known as the cross machine direction and which is right angle to the direction the wire 36 is moving fig2 illustrates important machine and jet parameters associated with the jet 23 trajectory this is in the area just downstream of the headbox 21 and the breast roll 27 and for which the wire 26 is supported by the forming board 30 the parameters are defined as follows a b slice opening b t jet thickness at the vena contracta c t 2 thickness of the slurry 2 above the wire 6 moving horizontally in direction 13 d t 3 the thickness of the slurry 2 that is directed down in the direction 11 and is split at the leading edge of the lead blade 9 e d the distance from the leading edge of the lead blade 9 to the edge of the bottom slice lip 5 f h the height of the top surface of the bottom slice lip 5 to the top surface of the wire 6 g i the bottom slice lip 5 extension beyond the top slice lip 4 edge an explanation of the physics used to analyze the jet 23 trajectory is given in various textbooks one such reference.