one of the documented procedures in this installation of the ACS
ad_custom_form   return_url   item_group   item
What it does:
sets up the head of a form to feed to /tools/form-custom.tcl
Defined in: /web/philip/packages/acs-core/table-display-procs.tcl

Source code:

    append html "<form method=get action=\"/tools/form-custom\">\n" 
    if {![empty_string_p $return_url]} {
        append html "[export_form_vars return_url]\n"
    if {[empty_string_p $item_group]} {
        set item_group [ns_conn url]
    set item_original $item
    append html "[export_form_vars item_group item item_original]\n"
    append html "<input type=submit value=\"Save settings\">"