The rules that use the vocabulary item "at" are:

<normalize_pvd_operation>

center terrain at standard scale

<vector>

<vector_directive> at <point_name>

<vector_directive-cap> at <point_name> <vector_purpose-cap>

<vector_directive-holding_point> at <point_name> <vector_purpose-holding_point>

<vector-has_destination-recursive>

<vector_directive> at <point_name>

<vector_directive-cap> at <point_name> <vector_purpose-cap>

<vector_directive-holding_point> at <point_name> <vector_purpose-holding_point>

<location_prep>

at

<temporal_control_method>

<sp> at <time_point>

at <time_point>

<contact_rel>

are at

at

is at

<bearing_mod-gapsout_null-gapsin_null>

pointing at <point_loc-gapsout_null-gapsin_null>

<on_order>

at my command