Block elements are used as a low value resistor element

Meander resistors are used as a high value resistor element, but in series with a top hat element that provides a reliable laser trim.

Note: when calculating the L/W of the total element, each right angle turn adds 0.5 to the total.

Top hat elements are used as a high value laser-trimmable resistor element

Design considerations for laser trimmed vs. non laser trimmed circuits
Thin Film Resistor elements should be designed at either 80% or 100% of final value according to the following guidelines:

Resistors with no laser trim should be designed at 100% of final value. Non-laser trimmed resistors are used to reduce cost and lead-time and provide a resistor value tolerance control of ±10% or greater.

Resistors with laser trim (tolerances < ± 10%) should be designed at 80% of final value to allow for laser up-trimming.