Planning a variable-density thinning prescription is not just a question of throwing together squares and rectangles of various sizes.
We start with a plan of what features we are trying to preserve -- such as large conifer snags and stumps or locations with plants sensitive
to disturbance -- and use that plan to locate our skips. We also need to consider the logging system which will be used so that skips do not
block access to areas we wish to thin (as skips are usually areas with no-equipment access). In general, gaps are not located next to skips so
that the unthinned skips will be as little disturbed as possible. For many projects, it may not be
necessary or desirable to include both skips and gaps in each unit. The planner may want to select some units for gaps and other units for skips
and only a few of the larger units might have both skips and gaps.