On-demand worker

i have another job in addition to a translation work at home.
About 5 to 6 times a month, i go off to a company, which offers various services to dentists as a dental-related supplier (supplier of drugs, diagnosis tools and as medical practice consultant. i'm in charge of graphic design work with a computer. Each time my bussiness occurs, i am called to the compnay. Now this is what I call "On-demand worker".
Today, after finishing my job, i went to the company at about PM2:00. Creating name seals to be sealed to a dental clinic car and updating web pages.　Finishing my work at PM6:00, i returned home. Agreeable fatigue.