Resources for labor in project

Create hammock activity and assign 2 engineers on this hammock that lasts from the start to the finish of your project (subproject). Don't assign these engineers to other activities.

thannnks for your idea.I used it now and it verrry easy >>

In case the resources shall be assigned full time to certain activities these must be leveled so the activities will not happen at the same time; the hammock can be resource loaded with variable workload and min workload equal to 0.  In this way when not assigned to any specific activity it will be assigned to the hammock.

The most common HORROR I have seen is to assign a crane to a hammock and not resource level it, there is a limit on how much work a crane can do on a single day!