the density of the secondary substrate 39 s material in another preferred embodiment the relative approximate density of the primary substrate 39 s material should be 15 or less than the density of the secondary substrate 39 s material while specific materials have been discussed other materials which provide these advantages can also be used for the substrates the surface area of each secondary substrate 7 is greater than the surface area of a portion 30 of the rule 8 that contacts it as shown in the figures the secondary substrate extends along and contacts substantially all of the rule 8 while supporting it as the rule 8 is pressed against the secondary substrate 7 the force of the load is distributed over the surface area of the secondary substrate 7 and then to the portion of the primary substrate 1 contacting the secondary substrate 7 this distribution of the load reduces the magnitude of the load applied to any one location on the primary substrate 1 thereby preventing damage to the primary substrate 1 therefore along with preventing the rule 8 from diving into the secondary substrate 7 the hard secondary substrate 7 also reduces the magnitude and effect of a cutting load applied to the rule 8 on the primary substrate 1.