Background: Staff may encourage individuals with intellectual disabilities to use manual signs by modelling its use, but implementing key word signing during daily activities can be demanding. Method: Staff's use of manual signs was observed in four special schools and four day centres for adults with intellectual disabilities during communicative group activities, non-communicative group activities and mealtimes. Using "in situ" partial interval coding, we measured staff's communication rate, semantic diversity of manual signs, sign reinforcement and sign imitation. With Chi-squared tests, associations were measured between these variables, the two settings and the three activity types. Results: During communicative activities, staff used manual signs significantly more in adult services than special schools. During non-communicative activities and mealtimes, staff seldom used or reinforced signs. Conclusions: Staff communicated frequently but did not often model sign use during daily activities. To investigate influence from training background, further detailed measurements are warranted.