Usually, the access log has the value for each field under the format but sometimes there is a requirement to just have a fixed character in the access log like a "-" hyphen.
Release : 6.7.x and 7.x
Component : Access Logging.
Add the "x-bluecoat-placeholder" field name under the access logging format to have the "-" (hyphen) as the value.
Go to Configuration > Access Logging > Formats.
Then Edit/View the format that you would like to have the "-" (hyphen) as the value and add the the "x-bluecoat-placeholder" field name.
The screen shot below shows an example for the 'main' access log.