In large construction projects such as skyscrapers, crane machines are essential. In project architecture and civil engineering, construction is the building or assembly of any infrastructure on a site or sites. Although this may not be thought of as a single activity, in fact construction is a feat of multitasking. Normally the job is managed by the construction manager and supervised by the project manager, design engineer or project architect. For the successful execution of a project, effective planning is essential. Those involved with the design and execution of the infrastructure in question must consider the environmental impact of the job, the successful scheduling, budgeting, site safety, availability of materials, logistics, inconvenience to the public caused by construction delays, preparing tender documents, etc.